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Metal Binding Proteins 2020

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A special issue of Biomolecules (ISSN 2218-273X). This special issue belongs to the section "Cellular Biochemistry".

Deadline for manuscript submissions: closed (30 September 2020) | Viewed by 52092

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Dr. Eugene A. Permyakov

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Institute for Biological Instrumentation, Russian Academy of Sciences, 142290 Pushchino, Russia
Interests: protein physics; luminescence (fluorescence, phosphorescence) spectroscopy of proteins; scanning and titration calorimetry of proteins; metal binding proteins; calcium binding proteins
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Dear Colleagues,

Everyone knows that the functioning of any biological system is impossible without metal ions. The ‘metals of life’ include sodium, potassium, magnesium, calcium, manganese, iron, cobalt, zinc, nickel, vanadium, molybdenum, and tungsten. Any biological system contains special proteins specifically interacting with metal ions. Metal ions play several major roles in proteins: structural, regulatory, and enzymatic. Strong binding of some metal ions increases the stability of proteins or protein domains. Some metal ions can regulate various cell processes being first, second or third messengers. Calcium is the most universal carrier of signals to cells. It regulates all important aspects of cell activity, beginning with fertilization and ending with apoptotic suicide at the end of the life cycle. Metal ions are an essential part of many enzymes and are indispensable in many catalytic reactions.

Despite the apparent good knowledge of the structure and properties of many metal-binding proteins, many aspects of their structure and, in particular, mechanisms of their functioning are still insufficiently studied. For example, although the three-dimensional structure of many calcium-binding sites in proteins is well known, a closer look at their environment reveals common structural features in these proteins that were not previously noticed. Studying the interactions of metal binding proteins with proteins of other classes allows us to reach a better understanding of their physiological functions. Modern methods of genetic engineering and knowledge of the three-dimensional structure of metal-binding proteins allow us to study their structure and functions at a new level. The obtained fundamental knowledge can already be used in applied science. Comprehensive reviews or original research articles are most welcome.

Dr. Eugene A. Permyakov
Guest Editor

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Keywords

metal ions
metal binding proteins
regulation
enzymes
structure
function

Published Papers (14 papers)

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12 pages, 1777 KiB

Open AccessCommunication

Gingival Crevicular Fluid Zinc- and Aspartyl-Binding Protease Profile of Individuals with Moderate/Severe Atopic Dermatitis

by Fernando Valenzuela, Javier Fernández, Marcela Aroca, Constanza Jiménez, Daniela Albers, Marcela Hernández and Alejandra Fernández

Biomolecules 2020, 10(12), 1600; https://0-doi-org.brum.beds.ac.uk/10.3390/biom10121600 - 26 Nov 2020

Cited by 10 | Viewed by 2587

Abstract

Atopic dermatitis (AD) is a protease-modulated chronic disorder with heterogenous clinical manifestations which may lead to an imprecise diagnosis. To date, there are no diagnostic protease tests for AD. We explored the gingival crevicular fluid (GCF) protease profile of individuals with moderate/severe AD compared to healthy controls. An exploratory case-control study was conducted. AD patients (n = 23) and controls (n = 21) were enrolled at the International Center for Clinical Studies, Santiago, Chile. Complete dermatological and periodontal evaluations (involving the collection of GCF samples) were made. The levels of 35 proteases were analyzed using a human protease antibody array in matching AD patients (n = 6) and controls (n = 6) with healthy periodontium. The GCF levels of zinc-binding ADAM8, ADAM9, MMP8, Neprilysin/CD10, aspartyl-binding Cathepsin E, serin-binding Protein convertase9, and uPA/Urokinase proteases were lower in moderate/severe AD patients compared to controls (p < 0.05). No inter-group differences in the levels of the other 28 proteases were found. MMP8, Cathepsin E, and ADAM9 were the biomarkers with the highest sensitivity and specificity regarding the detection of AD (p < 0.05). The area under receiver operating characteristic (ROC) curve for MMP8 was 0.83 and MMP8 + ADAMP9 was 0.90, with no significant differences (p = 0.132). A combined model of MMP8, Cathepsin E, and ADAM9 was not considered since it did not converge. Then, levels of MMP8 in GCF were determined using a multiplex bead immunoassay in 23 subjects with AD and 21 healthy subjects. Lower levels of MMP8 in the GCF from the AD group versus healthy group (p = 0.029) were found. This difference remained significant after adjustment by periodontitis (p = 0.042). MMP8 revealed the diagnostic potential to identify AD patients versus healthy controls, (ROC area = 0.672, p < 0.05). In conclusion, differences in the protease profile between AD and control patients were associated with MMP8, Cathepsin E, and ADAM9. Based on the multiplex assay results, MMP8 was lower in AD patients than controls, suggesting that MMP8 may be a diagnostic biomarker candidate. Full article

(This article belongs to the Special Issue Metal Binding Proteins 2020)

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13 pages, 2588 KiB

Open AccessArticle

MMP-8, TRAP-5, and OPG Levels in GCF Diagnostic Potential to Discriminate between Healthy Patients’, Mild and Severe Periodontitis Sites

by Marcela Hernández, Mauricio Baeza, Johanna Contreras, Timo Sorsa, Taina Tervahartiala, Macarena Valdés, Alejandra Chaparro and Patricia Hernández-Ríos

Biomolecules 2020, 10(11), 1500; https://0-doi-org.brum.beds.ac.uk/10.3390/biom10111500 - 30 Oct 2020

Cited by 7 | Viewed by 2405

Abstract

Biomarkers represent promising aids in periodontitis, host-mediate diseases of the tooth-supporting tissues. We assessed the diagnostic potential of matrix metalloproteinase-8 (MMP-8), tartrate-resistant acid phosphatase-5 (TRAP-5), and osteoprotegerin (OPG) to discriminate between healthy patients’, mild and severe periodontitis sites. Thirty-one otherwise healthy volunteers with and without periodontal disease were enrolled at the Faculty of Dentistry, University of Chile. Periodontal parameters were examined and gingival crevicular fluid was sampled from mild periodontitis sites (M; n = 42), severe periodontitis sites (S; n = 59), and healthy volunteer sites (H; n = 30). TRAP-5 and OPG were determined by commercial multiplex assay and MMP-8 by the immunofluorometric (IFMA) method. STATA software was used. All biomarkers showed a good discrimination performance. MMP-8 had the overall best performance in regression models and Receiver Operating Characteristic (ROC) curves, with high discrimination of healthy from periodontitis sites (area under the curve (AUC) = 0.901). OPG showed a very high diagnostic precision (AUC ≥ 0.95) to identify severe periodontitis sites (S versus H + M), while TRAP-5 identified both healthy and severe sites. As conclusions, MMP-8, TRAP-5, and OPG present a high precision potential in the identification of periodontal disease destruction, with MMP-8 as the most accurate diagnostic biomarker. Full article

(This article belongs to the Special Issue Metal Binding Proteins 2020)

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17 pages, 2887 KiB

Open AccessEditor’s ChoiceArticle

Modulation of Guanylate Cyclase Activating Protein 1 (GCAP1) Dimeric Assembly by Ca²⁺ or Mg²⁺: Hints to Understand Protein Activity

by Francesco Bonì, Valerio Marino, Carlo Bidoia, Eloise Mastrangelo, Alberto Barbiroli, Daniele Dell’Orco and Mario Milani

Biomolecules 2020, 10(10), 1408; https://0-doi-org.brum.beds.ac.uk/10.3390/biom10101408 - 05 Oct 2020

Cited by 9 | Viewed by 2832

Abstract

The guanylyl cyclase-activating protein 1, GCAP1, activates or inhibits retinal guanylyl cyclase (retGC) depending on cellular Ca²⁺ concentrations. Several point mutations of GCAP1 have been associated with impaired calcium sensitivity that eventually triggers progressive retinal degeneration. In this work, we demonstrate that the recombinant human protein presents a highly dynamic monomer-dimer equilibrium, whose dissociation constant is influenced by salt concentration and, more importantly, by protein binding to Ca²⁺ or Mg²⁺. Based on small-angle X-ray scattering data, protein-protein docking, and molecular dynamics simulations we propose two novel three-dimensional models of Ca²⁺-bound GCAP1 dimer. The different propensity of human GCAP1 to dimerize suggests structural differences induced by cation binding potentially involved in the regulation of retGC activity. Full article

(This article belongs to the Special Issue Metal Binding Proteins 2020)

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17 pages, 1906 KiB

Open AccessArticle

Expression and Purification of Recombinant GHK Tripeptides Are Able to Protect against Acute Cardiotoxicity from Exposure to Waterborne-Copper in Zebrafish

by Chung-Der Hsiao, Hsin-Hui Wu, Nemi Malhotra, Yen-Ching Liu, Ying-Hsuan Wu, Yu-Nung Lin, Ferry Saputra, Fiorency Santoso and Kelvin H.-C. Chen

Biomolecules 2020, 10(9), 1202; https://0-doi-org.brum.beds.ac.uk/10.3390/biom10091202 - 19 Aug 2020

Cited by 9 | Viewed by 4245

Abstract

In this study, an alternative method is developed to replace chemical synthesis to produce glycyl-histidyl-lysine (GHK) tripeptides with a bacterial fermentation system. The target GHK tripeptides are cloned into expression plasmids carrying histidine-glutathione-S-transferase (GST) double tags and TEV (tobacco etch virus) cleavage sites at the N-terminus. After overexpression in Escherichia coli (E. coli) BL21 cells, the recombinant proteins are purified and recovered by high-pressure liquid chromatography (HPLC). UV-vis absorption spectroscopy was used to investigate the chemical and biological properties of the recombinant GHK tripeptides. The results demonstrated that one recombinant GHK tripeptide can bind one copper ion to form a GHK-Cu complex with high affinity, and the recombinant GHK peptide to copper ion ratio is 1:1. X-ray absorption near-edge spectroscopy (XANES) of the copper ions indicated that the oxidation state of copper in the recombinant GHK-Cu complexes here was Cu(II). All of the optical spectrum evidence suggests that the recombinant GHK tripeptide appears to possess the same biophysical and biochemical features as the GHK tripeptide isolated from human plasma. Due to the high binding affinity of GHK tripeptides to copper ions, we used zebrafish as an in vivo model to elucidate whether recombinant GHK tripeptides possess detoxification potential against the cardiotoxicity raised by waterborne Cu(II) exposure. Here, exposure to Cu(II) induced bradycardia and heartbeat irregularity in zebrafish larvae; however, the administration of GHK tripeptides could rescue those experiencing cardiotoxicity, even at the lowest concentration of 1 nM, where the GHK-Cu complex minimized CuSO₄-induced cardiotoxicity effects at a GHK:Cu ratio of 1:10. On the other hand, copper and the combination with the GHK tripeptide did not significantly alter other cardiovascular parameters, including stroke volume, ejection fraction, and fractional shortening. Meanwhile, the heart rate and cardiac output were boosted after exposure with 1 nM of GHK peptides. In this study, recombinant GHK tripeptide expression was performed, along with purification and chemical property characterization, which revealed a potent cardiotoxicity protection function in vivo with zebrafish for the first time. Full article

(This article belongs to the Special Issue Metal Binding Proteins 2020)

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14 pages, 2847 KiB

Open AccessArticle

Structural Features Mediating Zinc Binding and Transfer in the AztABCD Zinc Transporter System

by Anusha Meni and Erik T. Yukl

Biomolecules 2020, 10(8), 1156; https://0-doi-org.brum.beds.ac.uk/10.3390/biom10081156 - 06 Aug 2020

Cited by 5 | Viewed by 2688

Abstract

Many bacteria require ATP binding cassette (ABC) transporters for the import of the essential metal zinc from limited environments. These systems rely on a periplasmic or cell-surface solute binding protein (SBP) to bind zinc with high affinity and specificity. AztABCD is one such zinc transport system recently identified in a large group of diverse bacterial species. In addition to a classical SBP (AztC), the operon also includes a periplasmic metallochaperone (AztD) shown to transfer zinc directly to AztC. Crystal structures of both proteins from Paracoccus denitrificans have been solved and suggest several structural features on each that may be important for zinc binding and transfer. Here we determine zinc binding affinity, dissociation kinetics, and transfer kinetics for several deletion mutants as well as a crystal structure for one of them. The results indicate specific roles for loop structures on AztC and an N-terminal motif on AztD in zinc binding and transfer. These data are consistent with a structural transfer model proposed previously and provide further mechanistic insight into the processes of zinc binding and transfer. Full article

(This article belongs to the Special Issue Metal Binding Proteins 2020)

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19 pages, 8060 KiB

Open AccessArticle

Distinct Calcium Binding and Structural Properties of Two Centrin Isoforms from Toxoplasma gondii

by Luca Bombardi, Marco Pedretti, Carolina Conter, Paola Dominici and Alessandra Astegno

Biomolecules 2020, 10(8), 1142; https://0-doi-org.brum.beds.ac.uk/10.3390/biom10081142 - 04 Aug 2020

Cited by 7 | Viewed by 2252

Abstract

Centrins are calcium (Ca²⁺)-binding proteins that have been implicated in several regulatory functions. In the protozoan parasite Toxoplasma gondii, the causative agent of toxoplasmosis, three isoforms of centrin have been identified. While increasing information is now available that links the function of centrins with defined parasite biological processes, knowledge is still limited on the metal-binding and structural properties of these proteins. Herein, using biophysical and structural approaches, we explored the Ca²⁺ binding abilities and the subsequent effects of Ca²⁺ on the structure of a conserved (TgCEN1) and a more divergent (TgCEN2) centrin isoform from T. gondii. Our data showed that TgCEN1 and TgCEN2 possess diverse molecular features, suggesting that they play nonredundant roles in parasite physiology. TgCEN1 binds two Ca²⁺ ions with high/medium affinity, while TgCEN2 binds one Ca²⁺ with low affinity. TgCEN1 undergoes significant Ca²⁺-dependent conformational changes that expose hydrophobic patches, supporting a role as a Ca²⁺ sensor in toxoplasma. In contrast, Ca²⁺ binding has a subtle influence on conformational features of TgCEN2 without resulting in hydrophobic exposure, suggesting a different Ca²⁺ relay mode for this isoform. Furthermore, TgCEN1 displays a Ca²⁺-dependent ability to self-assemble, while TgCEN2 did not. We discuss our findings in the context of Ca²⁺ signaling in toxoplasma. Full article

(This article belongs to the Special Issue Metal Binding Proteins 2020)

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22 pages, 2552 KiB

Open AccessArticle

A Novel Approach to Bacterial Expression and Purification of Myristoylated Forms of Neuronal Calcium Sensor Proteins

by Vasiliy I. Vladimirov, Viktoriia E. Baksheeva, Irina V. Mikhailova, Ramis G. Ismailov, Ekaterina A. Litus, Natalia K. Tikhomirova, Aliya A. Nazipova, Sergei E. Permyakov, Evgeni Yu. Zernii and Dmitry V. Zinchenko

Biomolecules 2020, 10(7), 1025; https://0-doi-org.brum.beds.ac.uk/10.3390/biom10071025 - 10 Jul 2020

Cited by 4 | Viewed by 3032

Abstract

N-terminal myristoylation is a common co-and post-translational modification of numerous eukaryotic and viral proteins, which affects their interaction with lipids and partner proteins, thereby modulating various cellular processes. Among those are neuronal calcium sensor (NCS) proteins, mediating transduction of calcium signals in a wide range of regulatory cascades, including reception, neurotransmission, neuronal growth and survival. The details of NCSs functioning are of special interest due to their involvement in the progression of ophthalmological and neurodegenerative diseases and their role in cancer. The well-established procedures for preparation of native-like myristoylated forms of recombinant NCSs via their bacterial co-expression with N-myristoyl transferase from Saccharomyces cerevisiae often yield a mixture of the myristoylated and non-myristoylated forms. Here, we report a novel approach to preparation of several NCSs, including recoverin, GCAP1, GCAP2, neurocalcin δ and NCS-1, ensuring their nearly complete N-myristoylation. The optimized bacterial expression and myristoylation of the NCSs is followed by a set of procedures for separation of their myristoylated and non-myristoylated forms using a combination of hydrophobic interaction chromatography steps. We demonstrate that the refolded and further purified myristoylated NCS-1 maintains its Ca²⁺-binding ability and stability of tertiary structure. The developed approach is generally suited for preparation of other myristoylated proteins. Full article

(This article belongs to the Special Issue Metal Binding Proteins 2020)

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11 pages, 1524 KiB

Open AccessArticle

The English (H6R) Mutation of the Alzheimer’s Disease Amyloid-β Peptide Modulates Its Zinc-Induced Aggregation

by Sergey P. Radko, Svetlana A. Khmeleva, Dmitry N. Kaluzhny, Olga I. Kechko, Yana Y. Kiseleva, Sergey A. Kozin, Vladimir A. Mitkevich and Alexander A. Makarov

Biomolecules 2020, 10(6), 961; https://0-doi-org.brum.beds.ac.uk/10.3390/biom10060961 - 25 Jun 2020

Cited by 6 | Viewed by 2394

Abstract

The coordination of zinc ions by histidine residues of amyloid-beta peptide (Aβ) plays a critical role in the zinc-induced Aβ aggregation implicated in Alzheimer’s disease (AD) pathogenesis. The histidine to arginine substitution at position 6 of the Aβ sequence (H6R, English mutation) leads to an early onset of AD. Herein, we studied the effects of zinc ions on the aggregation of the Aβ42 peptide and its isoform carrying the H6R mutation (H6R-Aβ42) by circular dichroism spectroscopy, dynamic light scattering, turbidimetric and sedimentation methods, and bis-ANS and thioflavin T fluorescence assays. Zinc ions triggered the occurrence of amorphous aggregates for both Aβ42 and H6R-Aβ42 peptides but with distinct optical properties. The structural difference of the formed Aβ42 and H6R-Aβ42 zinc-induced amorphous aggregates was also supported by the results of the bis-ANS assay. Moreover, while the Aβ42 peptide demonstrated an increase in the random coil and β-sheet content upon complexing with zinc ions, the H6R-Aβ42 peptide showed no appreciable structural changes under the same conditions. These observations were ascribed to the impact of H6R mutation on a mode of zinc/peptide binding. The presented findings further advance the understanding of the pathological role of the H6R mutation and the role of H6 residue in the zinc-induced Aβ aggregation. Full article

(This article belongs to the Special Issue Metal Binding Proteins 2020)

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17 pages, 4392 KiB

Open AccessArticle

Structure of the ALS Mutation Target Annexin A11 Reveals a Stabilising N-Terminal Segment

by Peder A. G. Lillebostad, Arne Raasakka, Silje J. Hjellbrekke, Sudarshan Patil, Trude Røstbø, Hanne Hollås, Siri A. Sakya, Peter D. Szigetvari, Anni Vedeler and Petri Kursula

Biomolecules 2020, 10(4), 660; https://0-doi-org.brum.beds.ac.uk/10.3390/biom10040660 - 24 Apr 2020

Cited by 8 | Viewed by 4952

Abstract

The functions of the annexin family of proteins involve binding to Ca²⁺, lipid membranes, other proteins, and RNA, and the annexins share a common folded core structure at the C terminus. Annexin A11 (AnxA11) has a long N-terminal region, which is predicted to be disordered, binds RNA, and forms membraneless organelles involved in neuronal transport. Mutations in AnxA11 have been linked to amyotrophic lateral sclerosis (ALS). We studied the structure and stability of AnxA11 and identified a short stabilising segment in the N-terminal end of the folded core, which links domains I and IV. The crystal structure of the AnxA11 core highlights main-chain hydrogen bonding interactions formed through this bridging segment, which are likely conserved in most annexins. The structure was also used to study the currently known ALS mutations in AnxA11. Three of these mutations correspond to buried Arg residues highly conserved in the annexin family, indicating central roles in annexin folding. The structural data provide starting points for detailed structure–function studies of both full-length AnxA11 and the disease variants being identified in ALS. Full article

(This article belongs to the Special Issue Metal Binding Proteins 2020)

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10 pages, 1362 KiB

Open AccessFeature PaperArticle

System Approach for Building of Calcium-Binding Sites in Proteins

by Alexander I. Denesyuk, Sergei E. Permyakov, Mark S. Johnson, Konstantin Denessiouk and Eugene A. Permyakov

Biomolecules 2020, 10(4), 588; https://0-doi-org.brum.beds.ac.uk/10.3390/biom10040588 - 11 Apr 2020

Viewed by 2235

Abstract

We introduce five new local metal cation (first of all, Ca²⁺) recognition units in proteins: Clamp_n,(n−2), Clamp_n,(n−1), Clamp_n,n, Clamp_n,(n+1) and Clamp_n,(n+2). In these units, the backbone oxygen atom of a residue in position “n” of an amino acid sequence and side-chain oxygen atom of a residue in position “n + i” (i = −2 to +2) directly interact with a metal cation. An analysis of the known “Ca²⁺-bound niches” in proteins has shown that a system approach based on the simultaneous use of the Clamp units and earlier proposed One-Residue (OR)/Three-Residue (TR) units significantly improves the results of constructing metal cation-binding sites in proteins. Full article

(This article belongs to the Special Issue Metal Binding Proteins 2020)

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21 pages, 3930 KiB

Open AccessArticle

Interactions Under Crowding Milieu: Chemical-Induced Denaturation of Myoglobin is Determined by the Extent of Heme Dissociation on Interaction with Crowders

by Khalida Nasreen, Zahoor Ahmad Parray, Shahzaib Ahamad, Faizan Ahmad, Anwar Ahmed, Salman Freeh Alamery, Tajamul Hussain, Md. Imtaiyaz Hassan and Asimul Islam

Biomolecules 2020, 10(3), 490; https://0-doi-org.brum.beds.ac.uk/10.3390/biom10030490 - 23 Mar 2020

Cited by 21 | Viewed by 4196

Abstract

Generally, in vivo function and structural changes are studied by probing proteins in a dilute solution under in vitro conditions, which is believed to be mimicking proteins in intracellular milieu. Earlier, thermal-induced denaturation of myoglobin, in the milieu of crowder molecule showed destabilization of the metal protein. Destabilization of protein by thermal-induced denaturation involves a large extrapolation, so, the reliability is questionable. This led us to measure the effects of macromolecular crowding on its stability by chemical-induced denaturation of the protein using probes like circular dichroism and absorption spectroscopy in the presence of dextran 70 and ficoll 70 at various pHs (acidic: 6.0, almost neutral: 7.0 and basic: 8.0). Observations showed that the degree of destabilization of myoglobin was greater due to ficoll 70 as compared to that of dextran 70 so it can be understood that the nature of the crowder or the shape of the crowder has an important role towards the stability of proteins. Additionally, the degree of destabilization was observed as pH dependent, however the pH dependence is different for different crowders. Furthermore, isothermal titration calorimetry and molecular docking studies confirmed that both the crowders (ficoll and dextran) bind to heme moiety of myoglobin and a single binding site was observed for each. Full article

(This article belongs to the Special Issue Metal Binding Proteins 2020)

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Review

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26 pages, 2143 KiB

Open AccessReview

Cellular Dynamics of Transition Metal Exchange on Proteins: A Challenge but a Bonanza for Coordination Chemistry

by Jean-Marc Moulis

Biomolecules 2020, 10(11), 1584; https://0-doi-org.brum.beds.ac.uk/10.3390/biom10111584 - 21 Nov 2020

Cited by 12 | Viewed by 3034

Abstract

Transition metals interact with a large proportion of the proteome in all forms of life, and they play mandatory and irreplaceable roles. The dynamics of ligand binding to ions of transition metals falls within the realm of Coordination Chemistry, and it provides the basic principles controlling traffic, regulation, and use of metals in cells. Yet, the cellular environment stands out against the conditions prevailing in the test tube when studying metal ions and their interactions with various ligands. Indeed, the complex and often changing cellular environment stimulates fast metal–ligand exchange that mostly escapes presently available probing methods. Reducing the complexity of the problem with purified proteins or in model organisms, although useful, is not free from pitfalls and misleading results. These problems arise mainly from the absence of the biosynthetic machinery and accessory proteins or chaperones dealing with metal / metal groups in cells. Even cells struggle with metal selectivity, as they do not have a metal-directed quality control system for metalloproteins, and serendipitous metal binding is probably not exceptional. The issue of metal exchange in biology is reviewed with particular reference to iron and illustrating examples in patho-physiology, regulation, nutrition, and toxicity. Full article

(This article belongs to the Special Issue Metal Binding Proteins 2020)

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50 pages, 3260 KiB

Open AccessReview

α-Lactalbumin, Amazing Calcium-Binding Protein

by Eugene A. Permyakov

Biomolecules 2020, 10(9), 1210; https://0-doi-org.brum.beds.ac.uk/10.3390/biom10091210 - 20 Aug 2020

Cited by 45 | Viewed by 8186

Abstract

α-Lactalbumin (α-LA) is a small (Mr 14,200), acidic (pI 4–5), Ca²⁺-binding protein. α-LA is a regulatory component of lactose synthase enzyme system functioning in the lactating mammary gland. The protein possesses a single strong Ca²⁺-binding site, which can also bind Mg²⁺, Mn²⁺, Na⁺, K⁺, and some other metal cations. It contains several distinct Zn²⁺-binding sites. Physical properties of α-LA strongly depend on the occupation of its metal binding sites by metal ions. In the absence of bound metal ions, α-LA is in the molten globule-like state. The binding of metal ions, and especially of Ca²⁺, increases stability of α-LA against the action of heat, various denaturing agents and proteases, while the binding of Zn²⁺ to the Ca²⁺-loaded protein decreases its stability and causes its aggregation. At pH 2, the protein is in the classical molten globule state. α-LA can associate with membranes at neutral or slightly acidic pH at physiological temperatures. Depending on external conditions, α-LA can form amyloid fibrils, amorphous aggregates, nanoparticles, and nanotubes. Some of these aggregated states of α-LA can be used in practical applications such as drug delivery to tissues and organs. α-LA and some of its fragments possess bactericidal and antiviral activities. Complexes of partially unfolded α-LA with oleic acid are cytotoxic to various tumor and bacterial cells. α-LA in the cytotoxic complexes plays a role of a delivery carrier of cytotoxic fatty acid molecules into tumor and bacterial cells across the cell membrane. Perhaps in the future the complexes of α-LA with oleic acid will be used for development of new anti-cancer drugs. Full article

(This article belongs to the Special Issue Metal Binding Proteins 2020)

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16 pages, 2677 KiB

Open AccessReview

Uranyl Binding to Proteins and Structural-Functional Impacts

by Ying-Wu Lin

Biomolecules 2020, 10(3), 457; https://0-doi-org.brum.beds.ac.uk/10.3390/biom10030457 - 16 Mar 2020

Cited by 30 | Viewed by 5456

Abstract

The widespread use of uranium for civilian purposes causes a worldwide concern of its threat to human health due to the long-lived radioactivity of uranium and the high toxicity of uranyl ion (UO₂²⁺). Although uranyl–protein/DNA interactions have been known for decades, fewer advances are made in understanding their structural-functional impacts. Instead of focusing only on the structural information, this article aims to review the recent advances in understanding the binding of uranyl to proteins in either potential, native, or artificial metal-binding sites, and the structural-functional impacts of uranyl–protein interactions, such as inducing conformational changes and disrupting protein-protein/DNA/ligand interactions. Photo-induced protein/DNA cleavages, as well as other impacts, are also highlighted. These advances shed light on the structure-function relationship of proteins, especially for metalloproteins, as impacted by uranyl–protein interactions. It is desired to seek approaches for biological remediation of uranyl ions, and ultimately make a full use of the double-edged sword of uranium. Full article

(This article belongs to the Special Issue Metal Binding Proteins 2020)

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