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11 pages, 2757 KiB

Open AccessArticle

Improved Solubility and Stability of a Thermostable Carbonic Anhydrase via Fusion with Marine-Derived Intrinsically Disordered Solubility Enhancers

by Byung Hoon Jo

Int. J. Mol. Sci. 2024, 25(2), 1139; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms25021139 - 17 Jan 2024

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Abstract

Carbonic anhydrase (CA), an enzyme catalyzing the reversible hydration reaction of carbon dioxide (CO₂), is considered a promising biocatalyst for CO₂ reduction. The α-CA of Thermovibrio ammonificans (taCA) has emerged as a compelling candidate due to its high thermostability, a [...] Read more.

Carbonic anhydrase (CA), an enzyme catalyzing the reversible hydration reaction of carbon dioxide (CO₂), is considered a promising biocatalyst for CO₂ reduction. The α-CA of Thermovibrio ammonificans (taCA) has emerged as a compelling candidate due to its high thermostability, a critical factor for industrial applications. However, the low-level expression and poor in vitro solubility have hampered further utilization of taCA. Recently, these limitations have been addressed through the fusion of the NEXT tag, a marine-derived, intrinsically disordered small peptide that enhances protein expression and solubility. In this study, the solubility and stability of NEXT-taCA were further investigated. When the linker length between the NEXT tag and the taCA was shortened, the expression level decreased without compromising solubility-enhancing performance. A comparison between the NEXT tag and the NT11 tag demonstrated the NEXT tag’s superiority in improving both the expression and solubility of taCA. While the thermostability of taCA was lower than that of the extensively engineered DvCA10, the NEXT-tagged taCA exhibited a 30% improvement in long-term thermostability compared to the untagged taCA, suggesting that enhanced solubility can contribute to enzyme thermostability. Furthermore, the bioprospecting of two intrinsically disordered peptides (Hcr and Hku tags) as novel solubility-enhancing fusion tags was explored, demonstrating their performance in improving the expression and solubility of taCA. These efforts will advance the practical application of taCA and provide tools and insights for enzyme biochemistry and bioengineering. Full article

(This article belongs to the Special Issue Protein Stability Research)

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16 pages, 2393 KiB

Open AccessArticle

The Pivotal Distinction between Antagonists’ and Agonists’ Binding into Dopamine D4 Receptor—MD and FMO/PIEDA Studies

by Paweł Śliwa, Magdalena Dziurzyńska, Rafał Kurczab and Katarzyna Kucwaj-Brysz

Int. J. Mol. Sci. 2024, 25(2), 746; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms25020746 - 06 Jan 2024

Viewed by 1059

Abstract

The dopamine D4 receptor (D4R) is a promising therapeutic target in widespread diseases, and the search for novel agonists and antagonists appears to be clinically relevant. The mechanism of binding to the receptor (R) for antagonists and agonists varies. In the present study, [...] Read more.

The dopamine D4 receptor (D4R) is a promising therapeutic target in widespread diseases, and the search for novel agonists and antagonists appears to be clinically relevant. The mechanism of binding to the receptor (R) for antagonists and agonists varies. In the present study, we conducted an in-depth computational study, teasing out key similarities and differences in binding modes, complex dynamics, and binding energies for D4R agonists and antagonists. The dynamic network method was applied to investigate the communication paths between the ligand (L) and G-protein binding site (GBS) of human D4R. Finally, the fragment molecular orbitals with pair interaction energy decomposition analysis (FMO/PIEDA) scheme was used to estimate the binding energies of L–R complexes. We found that a strong salt bridge with D3.32 initiates the inhibition of the dopamine D4 receptor. This interaction also occurs in the binding of agonists, but the change in the receptor conformation to the active state starts with interaction with cysteine C3.36. Such a mechanism may arise in the case of agonists unable to form a hydrogen bond with the serine S5.46, considered, so far, to be crucial in the activation of GPCRs. The energy calculations using the FMO/PIEDA method indicate that antagonists show higher residue occupancy of the receptor binding site than agonists, suggesting they could form relatively more stable complexes. Additionally, antagonists were characterized by repulsive interactions with S5.46 distinguishing them from agonists. Full article

(This article belongs to the Special Issue Protein Stability Research)

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19 pages, 3739 KiB

Open AccessArticle

Effect of Chemical Chaperones on the Stability of Proteins during Heat– or Freeze–Thaw Stress

by Vera A. Borzova, Tatiana B. Eronina, Valeriya V. Mikhaylova, Svetlana G. Roman, Andrey M. Chernikov and Natalia A. Chebotareva

Int. J. Mol. Sci. 2023, 24(12), 10298; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms241210298 - 18 Jun 2023

Cited by 2 | Viewed by 1060

Abstract

The importance of studying the structural stability of proteins is determined by the structure–function relationship. Protein stability is influenced by many factors among which are freeze–thaw and thermal stresses. The effect of trehalose, betaine, sorbitol and 2-hydroxypropyl-β-cyclodextrin (HPCD) on the stability and aggregation [...] Read more.

The importance of studying the structural stability of proteins is determined by the structure–function relationship. Protein stability is influenced by many factors among which are freeze–thaw and thermal stresses. The effect of trehalose, betaine, sorbitol and 2-hydroxypropyl-β-cyclodextrin (HPCD) on the stability and aggregation of bovine liver glutamate dehydrogenase (GDH) upon heating at 50 °C or freeze–thawing was studied by dynamic light scattering, differential scanning calorimetry, analytical ultracentrifugation and circular dichroism spectroscopy. A freeze–thaw cycle resulted in the complete loss of the secondary and tertiary structure, and aggregation of GDH. All the cosolutes suppressed freeze–thaw- and heat-induced aggregation of GDH and increased the protein thermal stability. The effective concentrations of the cosolutes during freeze–thawing were lower than during heating. Sorbitol exhibited the highest anti-aggregation activity under freeze–thaw stress, whereas the most effective agents stabilizing the tertiary structure of GDH were HPCD and betaine. HPCD and trehalose were the most effective agents suppressing GDH thermal aggregation. All the chemical chaperones stabilized various soluble oligomeric forms of GDH against both types of stress. The data on GDH were compared with the effects of the same cosolutes on glycogen phosphorylase b during thermal and freeze–thaw-induced aggregation. This research can find further application in biotechnology and pharmaceutics. Full article

(This article belongs to the Special Issue Protein Stability Research)

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20 pages, 4842 KiB

Open AccessArticle

Molecular Dynamics Simulations of HPr Proteins from a Thermophilic and a Mesophilic Organism: A Comparative Thermal Study

by Ana K. Gómez-Flores, Edgar López-Pérez and Salomón J. Alas-Guardado

Int. J. Mol. Sci. 2023, 24(11), 9557; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms24119557 - 31 May 2023

Viewed by 1156

Abstract

The histidine-containing phosphocarrier (HPr) is a monomeric protein conserved in Gram-positive bacteria, which may be of mesophilic or thermophilic nature. In particular, the HPr protein from the thermophilic organism B. stearothermophilus is a good model system for thermostability studies, since experimental data, such [...] Read more.

The histidine-containing phosphocarrier (HPr) is a monomeric protein conserved in Gram-positive bacteria, which may be of mesophilic or thermophilic nature. In particular, the HPr protein from the thermophilic organism B. stearothermophilus is a good model system for thermostability studies, since experimental data, such as crystal structure and thermal stability curves, are available. However, its unfolding mechanism at higher temperatures is yet unclear at a molecular level. Therefore, in this work, we researched the thermal stability of this protein using molecular dynamics simulations, subjecting it to five different temperatures during a time span of 1 μs. The analyses of the structural parameters and molecular interactions were compared with those of the mesophilic homologue HPr protein from B. subtilis. Each simulation was run in triplicate using identical conditions for both proteins. The results showed that the two proteins lose stability as the temperature increases, but the mesophilic structure is more affected. We found that the salt bridge network formed by the triad of Glu3-Lys62-Glu36 residues and the salt bridge made up of Asp79-Lys83 ion pair are key factors to keep stable the thermophilic protein, maintaining the hydrophobic core protected and the structure packed. In addition, these molecular interactions neutralize the negative surface charge, acting as “natural molecular staples”. Full article

(This article belongs to the Special Issue Protein Stability Research)

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31 pages, 8686 KiB

Open AccessArticle

Coarse-Grained Molecular Simulations and Ensemble-Based Mutational Profiling of Protein Stability in the Different Functional Forms of the SARS-CoV-2 Spike Trimers: Balancing Stability and Adaptability in BA.1, BA.2 and BA.2.75 Variants

by Gennady Verkhivker, Mohammed Alshahrani and Grace Gupta

Int. J. Mol. Sci. 2023, 24(7), 6642; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms24076642 - 02 Apr 2023

Cited by 2 | Viewed by 1429

Abstract

Evolutionary and functional studies have suggested that the emergence of Omicron variants can be determined by multiple fitness tradeoffs including immune escape, binding affinity, conformational plasticity, protein stability, and allosteric modulation. In this study, we embarked on a systematic comparative analysis of the [...] Read more.

Evolutionary and functional studies have suggested that the emergence of Omicron variants can be determined by multiple fitness tradeoffs including immune escape, binding affinity, conformational plasticity, protein stability, and allosteric modulation. In this study, we embarked on a systematic comparative analysis of the conformational dynamics, electrostatics, protein stability, and allostery in the different functional states of spike trimers for BA.1, BA.2, and BA.2.75 variants. Using efficient and accurate coarse-grained simulations and atomistic reconstruction of the ensembles, we examined the conformational dynamics of the spike trimers that agree with the recent functional studies, suggesting that BA.2.75 trimers are the most stable among these variants. A systematic mutational scanning of the inter-protomer interfaces in the spike trimers revealed a group of conserved structural stability hotspots that play a key role in the modulation of functional dynamics and are also involved in the inter-protomer couplings through local contacts and interaction networks with the Omicron mutational sites. The results of mutational scanning provided evidence that BA.2.75 trimers are more stable than BA.2 and comparable in stability to the BA.1 variant. Using dynamic network modeling of the S Omicron BA.1, BA.2, and BA.2.75 trimers, we showed that the key network mediators of allosteric interactions are associated with the major stability hotspots that are interconnected along potential communication pathways. The network analysis of the BA.1, BA.2, and BA.2.75 trimers suggested that the increased thermodynamic stability of the BA.2.75 variant may be linked with the organization and modularity of the residue interaction network that allows for allosteric communications between structural stability hotspots and Omicron mutational sites. This study provided a plausible rationale for a mechanism in which Omicron mutations may evolve by targeting vulnerable sites of conformational adaptability to elicit immune escape while maintaining their control on balancing protein stability and functional fitness through robust allosteric communications with the stability hotspots. Full article

(This article belongs to the Special Issue Protein Stability Research)

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15 pages, 3443 KiB

Open AccessArticle

Comparison of Human Eukaryotic Translation Initiation Factors 5A1 and 5AL1: Identification of Amino Acid Residues Important for EIF5A1 Lysine 50 Hypusination and Its Protein Stability

by Yu-Yao Wu, Gao-Qi Wu, Na-Li Cai, Yan-Ming Xu and Andy T. Y. Lau

Int. J. Mol. Sci. 2023, 24(7), 6067; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms24076067 - 23 Mar 2023

Cited by 1 | Viewed by 1391

Abstract

The human eukaryotic translation initiation factor 5A (EIF5A) family consists of three members, namely EIF5A1, EIF5A2, and EIF5AL1. Recent studies have shown that the expression of EIF5As is related to many human diseases, such as diabetes, viral infection, central nervous system injury, and [...] Read more.

The human eukaryotic translation initiation factor 5A (EIF5A) family consists of three members, namely EIF5A1, EIF5A2, and EIF5AL1. Recent studies have shown that the expression of EIF5As is related to many human diseases, such as diabetes, viral infection, central nervous system injury, and cancer. Among them, EIF5A1 plays different functions in various cancers, possibly as a tumor-suppressor or oncogene, while EIF5A2 promotes the occurrence and development of cancer. Yet, the biological function of EIF5AL1 is not being studied so far. Interestingly, although there are only three amino acid (at residues 36, 45, and 109) differences between EIF5A1 and EIF5AL1, we demonstrate that only EIF5A1 can be hypusinated while EIF5AL1 cannot, and EIF5AL1 has a tumor-suppressor-like function by inhibiting cell proliferation and migration. We also show that EIF5AL1 protein turnover is mediated through the proteasomal pathway, and EIF5AL1 protein turnover is much faster than that of EIF5A1, which may explain their differential protein expression level in cells. By engineering single and double mutations on these three amino acids, we pinpoint which of these amino acids are critical for hypusination and protein stability. The data of this work should fill in the gaps in EIF5As research and pave the way for future studies on EIF5AL1. Full article

(This article belongs to the Special Issue Protein Stability Research)

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13 pages, 5031 KiB

Open AccessArticle

Solubility and Thermal Stability of Thermotoga maritima MreB

by Beáta Longauer, Emőke Bódis, András Lukács, Szilvia Barkó and Miklós Nyitrai

Int. J. Mol. Sci. 2022, 23(24), 16044; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms232416044 - 16 Dec 2022

Cited by 1 | Viewed by 1210

Abstract

The basis of MreB research is the study of the MreB protein from the Thermotoga maritima species, since it was the first one whose crystal structure was described. Since MreB proteins from different bacterial species show different polymerisation properties in terms of nucleotide [...] Read more.

The basis of MreB research is the study of the MreB protein from the Thermotoga maritima species, since it was the first one whose crystal structure was described. Since MreB proteins from different bacterial species show different polymerisation properties in terms of nucleotide and salt dependence, we conducted our research in this direction. For this, we performed measurements based on tryptophan emission, which were supplemented with temperature-dependent and chemical denaturation experiments. The role of nucleotide binding was studied through the fluorescent analogue TNP-ATP. These experiments show that Thermotoga maritima MreB is stabilised in the presence of low salt buffer and ATP. In the course of our work, we developed a new expression and purification procedure that allows us to obtain a large amount of pure, functional protein. Full article

(This article belongs to the Special Issue Protein Stability Research)

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30 pages, 1488 KiB

Open AccessReview

The Function, Regulation, and Mechanism of Protein Turnover in Circadian Systems in Neurospora and Other Species

by Haoran Zhang, Zengxuan Zhou and Jinhu Guo

Int. J. Mol. Sci. 2024, 25(5), 2574; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms25052574 - 22 Feb 2024

Viewed by 876

Abstract

Circadian clocks drive a large array of physiological and behavioral activities. At the molecular level, circadian clocks are composed of positive and negative elements that form core oscillators generating the basic circadian rhythms. Over the course of the circadian period, circadian negative proteins [...] Read more.

Circadian clocks drive a large array of physiological and behavioral activities. At the molecular level, circadian clocks are composed of positive and negative elements that form core oscillators generating the basic circadian rhythms. Over the course of the circadian period, circadian negative proteins undergo progressive hyperphosphorylation and eventually degrade, and their stability is finely controlled by complex post-translational pathways, including protein modifications, genetic codon preference, protein–protein interactions, chaperon-dependent conformation maintenance, degradation, etc. The effects of phosphorylation on the stability of circadian clock proteins are crucial for precisely determining protein function and turnover, and it has been proposed that the phosphorylation of core circadian clock proteins is tightly correlated with the circadian period. Nonetheless, recent studies have challenged this view. In this review, we summarize the research progress regarding the function, regulation, and mechanism of protein stability in the circadian clock systems of multiple model organisms, with an emphasis on Neurospora crassa, in which circadian mechanisms have been extensively investigated. Elucidation of the highly complex and dynamic regulation of protein stability in circadian clock networks would greatly benefit the integrated understanding of the function, regulation, and mechanism of protein stability in a wide spectrum of other biological processes. Full article

(This article belongs to the Special Issue Protein Stability Research)

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