A Snake Venom Peptide and Its Derivatives Prevent Aß42 Aggregation and Eliminate Toxic Aß42 Aggregates In Vitro.

Over a century has passed since Alois Alzheimer first described Alzheimer's disease (AD), and since then, researchers have made significant strides in understanding its pathology. One key feature of AD is the presence of amyloid-ß (Aß) peptides, which form amyloid plaques, and therefore, it is a primary target for treatment studies. Naturally occurring peptides have garnered attention for their potential pharmacological benefits, particularly in the central nervous system. In this study, nine peptide derivatives of Crotamine, a polypeptide from Crotalus durissus terrificus Rattlesnake venom, as well as one d-enantiomer, were evaluated for their ability to modulate Aß42 aggregation through various assays such as ThT, QIAD, SPR, and sFIDA. All tested peptides were able to decrease Aß42 aggregation and eliminate Aß42 aggregates. Additionally, all of the peptides showed an affinity for Aß42. This study is the first to describe the potential of crotamine derivative peptides against Aß42 aggregation and to identify a promising d-peptide that could be used as an effective pharmacological tool against AD in the future.

HR-MAS NMR Metabolomics Profile of Vero Cells under the Influence of Virus Infection and nsP2 Inhibitor: A Chikungunya Case Study.

The arbovirus Chikungunya (CHIKV) is transmitted by Aedes mosquitoes in urban environments, and in humans, it triggers debilitating symptoms involving long-term complications, including arthritis and Guillain-Barré syndrome. The development of antiviral therapies is relevant, as no efficacious vaccine or drug has yet been approved for clinical application. As a detailed map of molecules underlying the viral infection can be obtained from the metabolome, we validated the metabolic signatures of Vero E6 cells prior to infection (CC), following CHIKV infection (CV) and also upon the inclusion of the nsP2 protease inhibitor wedelolactone (CWV), a coumestan which inhibits viral replication processes. The metabolome groups evidenced significant changes in the levels of lactate, myo-inositol, phosphocholine, glucose, betaine and a few specific amino acids. This study forms a preliminary basis for identifying metabolites through HR-MAS NMR (High Resolution Magic Angle Spinning Nuclear Magnetic Ressonance Spectroscopy) and proposing the affected metabolic pathways of cells following viral infection and upon incorporation of putative antiviral molecules.

The Importance of Epigallocatechin as a Scaffold for Drug Development against Flaviviruses.

Arboviruses such as Dengue, yellow fever, West Nile, and Zika are flaviviruses vector-borne RNA viruses transmitted biologically among vertebrate hosts by blood-taking vectors. Many flaviviruses are associated with neurological, viscerotropic, and hemorrhagic diseases, posing significant health and socioeconomic concerns as they adapt to new environments. Licensed drugs against them are currently unavailable, so searching for effective antiviral molecules is still necessary. Epigallocatechin molecules, a green tea polyphenol, have shown great virucidal potential against flaviviruses, including DENV, WNV, and ZIKV. The interaction of EGCG with the viral envelope protein and viral protease, mainly identified by computational studies, describes the interaction of these molecules with viral proteins; however, how the viral NS2B/NS3 protease interacts with epigallocatechin molecules is not yet fully deciphered. Consequently, we tested the antiviral potential of two epigallocatechin molecules (EGC and EGCG) and their derivative (AcEGCG) against DENV, YFV, WNV, and ZIKV NS2B/NS3 protease. Thus, we assayed the effect of the molecules and found that a mixture of the molecules EGC (competitive) and EGCG (noncompetitive) inhibited the virus protease of YFV, WNV, and ZIKV more effectively with IC50 values of 1.17 ± 0.2 µM, 0.58 ± 0.07 µM, and 0.57 ± 0.05 µM, respectively. As these molecules fundamentally differ in their inhibitory mode and chemical structure, our finding may open a new line for developing more effective allosteric/active site inhibitors to combat flaviviruses infection.

Discovery of All-d-Peptide Inhibitors of SARS-CoV-2 3C-like Protease.

During the replication process of SARS-CoV-2, the main protease of the virus [3-chymotrypsin-like protease (3CLpro)] plays a pivotal role and is essential for the life cycle of the pathogen. Numerous studies have been conducted so far, which have confirmed 3CLpro as an attractive drug target to combat COVID-19. We describe a novel and efficient next-generation sequencing (NGS) supported phage display selection strategy for the identification of a set of SARS-CoV-2 3CLpro targeting peptide ligands that inhibit the 3CL protease, in a competitive or noncompetitive mode, in the low µM range. From the most efficient l-peptides obtained from the phage display, we designed all-d-peptides based on the retro-inverso (ri) principle. They had IC50 values also in the low µM range and in combination, even in the sub-micromolar range. Additionally, the combination with Rutinprivir decreases 10-fold the IC50 value of the competitive inhibitor. The inhibition modes of these d-ri peptides were the same as their respective l-peptide versions. Our results demonstrate that retro-inverso obtained all-d-peptides interact with high affinity and inhibit the SARS-CoV-2 3CL protease, thus reinforcing their potential for further development toward therapeutic agents. The here described d-ri peptides address limitations associated with current l-peptide inhibitors and are promising lead compounds. Further optimization regarding pharmacokinetic properties will allow the development of even more potent d-peptides to be used for the prevention and treatment of COVID-19.

A Review of Omics Studies on Arboviruses: Alphavirus, Orthobunyavirus and Phlebovirus.

Since the intricate and complex steps in pathogenesis and host-viral interactions of arthropod-borne viruses or arboviruses are not completely understood, the multi-omics approaches, which encompass proteomics, transcriptomics, genomics and metabolomics network analysis, are of great importance. We have reviewed the omics studies on mosquito-borne viruses of the Togaviridae, Peribuyaviridae and Phenuiviridae families, specifically for Chikungunya, Mayaro, Oropouche and Rift Valley Fever viruses. Omics studies can potentially provide a new perspective on the pathophysiology of arboviruses, contributing to a better comprehension of these diseases and their effects and, hence, provide novel insights for the development of new antiviral drugs or therapies.

Riboflavin, a Potent Neuroprotective Vitamin: Focus on Flavivirus and Alphavirus Proteases.

Several neurotropic viruses are members of the flavivirus and alphavirus families. Infections caused by these viruses may cause long-term neurological sequelae in humans. The continuous emergence of infections caused by viruses around the world, such as the chikungunya virus (CHIKV) (Alphavirus genus), the zika virus (ZIKV) and the yellow fever virus (YFV) (both of the Flavivirus genus), warrants the development of new strategies to combat them. Our study demonstrates the inhibitory potential of the water-soluble vitamin riboflavin against NS2B/NS3pro of ZIKV and YFV and nsP2pro of CHIKV. Riboflavin presents a competitive inhibition mode with IC50 values in the medium µM range of 79.4 ± 5.0 µM for ZIKV NS2B/NS3pro and 45.7 ± 2.9 µM for YFV NS2B/NS3pro. Against CHIKV nsP2pro, the vitamin showed a very strong effect (93 ± 5.7 nM). The determined dissociation constants (KD) are significantly below the threshold value of 30 µM. The ligand binding increases the thermal stability between 4 °C and 8 °C. Unexpectedly, riboflavin showed inhibiting activity against another viral protein; the molecule was also able to inhibit the viral entry of CHIKV. Molecular dynamics simulations indicated great stability of riboflavin in the protease active site, which validates the repurposing of riboflavin as a promising molecule in drug development against the viruses presented here.

Design of D-Amino Acids SARS-CoV-2 Main Protease Inhibitors Using the Cationic Peptide from Rattlesnake Venom as a Scaffold.

The C30 endopeptidase (3C-like protease; 3CLpro) is essential for the life cycle of SARS-CoV-2 (severe acute respiratory syndrome-coronavirus-2) since it plays a pivotal role in viral replication and transcription and, hence, is a promising drug target. Molecules isolated from animals, insects, plants, or microorganisms can serve as a scaffold for the design of novel biopharmaceutical products. Crotamine, a small cationic peptide from the venom of the rattlesnake Crotalus durissus terrificus, has been the focus of many studies since it exhibits activities such as analgesic, in vitro antibacterial, and hemolytic activities. The crotamine derivative L-peptides (L-CDP) that inhibit the 3CL protease in the low µM range were examined since they are susceptible to proteolytic degradation; we explored the utility of their D-enantiomers form. Comparative uptake inhibition analysis showed D-CDP as a promising prototype for a D-peptide-based drug. We also found that the D-peptides can impair SARS-CoV-2 replication in vivo, probably targeting the viral protease 3CLpro.

Review of -omics studies on mosquito-borne viruses of the Flavivirus genus.

Arboviruses are transmitted by arthropods (arthropod-borne virus) which can be mosquitoes or other hematophagous arthropods, in which their life cycle occurs before transmission to other hosts. Arboviruses such as Dengue, Zika, Saint Louis Encephalitis, West Nile, Yellow Fever, Japanese Encephalitis, Rocio and Murray Valley Encephalitis viruses are some of the arboviruses transmitted biologically among vertebrate hosts by blood-taking vectors, mainly Aedes and Culex sp., and are associated with neurological, viscerotropic, and hemorrhagic reemerging diseases, posing as significant health and socioeconomic concern, as they become more and more adaptive to new environments, to arthropods vectors and human hosts. One of the main families that include mosquito-borne viruses is Flaviviridae, and here, we review the case of the Flavivirus genus, which comprises the viruses cited above, using a variety of research approaches published in literature, including genomics, transcriptomics, proteomics, metabolomics, etc., to better understand their structures as well as virus-host interactions, which are essential for development of future antiviral therapies.

Promising Natural Compounds against Flavivirus Proteases: Citrus Flavonoids Hesperetin and Hesperidin.

Ubiquitous in citrus plants, Hesperidin and Hesperetin flavanones possess several biological functions, including antiviral activity. Arbovirus infections pose an ever-increasing threat to global healthcare systems. Among the severe arboviral infections currently known are those caused by members of the Flavivirus genus, for example, Dengue Virus-DENV, Yellow Fever Virus-YFV, and West Nile Virus-WNV. In this study, we characterize the inhibitory effect of Hesperidin and Hesperetin against DENV2, YFV, and WNV NS2B/NS3 proteases. We report the noncompetitive inhibition of the NS2B/NS3pro by the two bioflavonoids with half maximal inhibitory concentration (IC50) values <5 µM for HST and <70 µM for HSD. The determined dissociation constants (KD) of both flavonoids is significantly below the threshold value of 30 µM. Our findings demonstrate that a new generation of anti-flavivirus drugs could be developed based on selective optimization of both molecules.

The Repurposed Drugs Suramin and Quinacrine Cooperatively Inhibit SARS-CoV-2 3CLpro In Vitro.

Since the first report of a new pneumonia disease in December 2019 (Wuhan, China) the WHO reported more than 148 million confirmed cases and 3.1 million losses globally up to now. The causative agent of COVID-19 (SARS-CoV-2) has spread worldwide, resulting in a pandemic of unprecedented magnitude. To date, several clinically safe and efficient vaccines (e.g., Pfizer-BioNTech, Moderna, Johnson & Johnson, and AstraZeneca COVID-19 vaccines) as well as drugs for emergency use have been approved. However, increasing numbers of SARS-Cov-2 variants make it imminent to identify an alternative way to treat SARS-CoV-2 infections. A well-known strategy to identify molecules with inhibitory potential against SARS-CoV-2 proteins is repurposing clinically developed drugs, e.g., antiparasitic drugs. The results described in this study demonstrated the inhibitory potential of quinacrine and suramin against SARS-CoV-2 main protease (3CLpro). Quinacrine and suramin molecules presented a competitive and noncompetitive inhibition mode, respectively, with IC50 values in the low micromolar range. Surface plasmon resonance (SPR) experiments demonstrated that quinacrine and suramin alone possessed a moderate or weak affinity with SARS-CoV-2 3CLpro but suramin binding increased quinacrine interaction by around a factor of eight. Using docking and molecular dynamics simulations, we identified a possible binding mode and the amino acids involved in these interactions. Our results suggested that suramin, in combination with quinacrine, showed promising synergistic efficacy to inhibit SARS-CoV-2 3CLpro. We suppose that the identification of effective, synergistic drug combinations could lead to the design of better treatments for the COVID-19 disease and repurposable drug candidates offer fast therapeutic breakthroughs, mainly in a pandemic moment.

Novel inhibitors of the main protease enzyme of SARS-CoV-2 identified via molecular dynamics simulation-guided in vitro assay.

For the COVID-19 pandemic caused by SARS-CoV-2, there are currently no effective drugs or vaccines to treat this coronavirus infection. In this study, we focus on the main protease enzyme of SARS-CoV-2, 3CLpro, which is critical for viral replication. We employ explicit solvent molecular dynamics simulations of about 150 compounds docked into 3CLpro's binding site and that had emerged as good main protease ligands from our previous in silico screening of over 1.2 million compounds. By incoporating protein dynamics and applying a range of structural descriptors, such as the ability to form specific contacts with the catalytic dyad residues of 3CLpro and the structural fluctuations of the ligands in the binding site, we are able to further refine our compound selection. Fourteen compounds including estradiol shown to be the most promising based on our calculations were procured and screened against recombinant 3CLpro in a fluorescence assay. Eight of these compounds have significant activity in inhibiting the SARS-CoV-2 main protease. Among these are corilagin, a gallotannin, and lurasidone, an antipsychotic drug, which emerged as the most promising natural product and drug, respectively, and might thus be candidates for drug repurposing for the treatment of COVID-19. In addition, we also tested the inhibitory activity of testosterone, and our results reveal testosterone as possessing moderate inhibitory potency against the 3CLpro enzyme, which may thus provide an explanation why older men are more severely affected by COVID-19.

In vitro study of Hesperetin and Hesperidin as inhibitors of zika and chikungunya virus proteases.

The potential outcome of flavivirus and alphavirus co-infections is worrisome due to the development of severe diseases. Hundreds of millions of people worldwide live under the risk of infections caused by viruses like chikungunya virus (CHIKV, genus Alphavirus), dengue virus (DENV, genus Flavivirus), and zika virus (ZIKV, genus Flavivirus). So far, neither any drug exists against the infection by a single virus, nor against co-infection. The results described in our study demonstrate the inhibitory potential of two flavonoids derived from citrus plants: Hesperetin (HST) against NS2B/NS3pro of ZIKV and nsP2pro of CHIKV and, Hesperidin (HSD) against nsP2pro of CHIKV. The flavonoids are noncompetitive inhibitors and the determined IC50 values are in low µM range for HST against ZIKV NS2B/NS3pro (12.6 ± 1.3 µM) and against CHIKV nsP2pro (2.5 ± 0.4 µM). The IC50 for HSD against CHIKV nsP2pro was 7.1 ± 1.1 µM. The calculated ligand efficiencies for HST were > 0.3, which reflect its potential to be used as a lead compound. Docking and molecular dynamics simulations display the effect of HST and HSD on the protease 3D models of CHIKV and ZIKV. Conformational changes after ligand binding and their effect on the substrate-binding pocket of the proteases were investigated. Additionally, MTT assays demonstrated a very low cytotoxicity of both the molecules. Based on our results, we assume that HST comprise a chemical structure that serves as a starting point molecule to develop a potent inhibitor to combat CHIKV and ZIKV co-infections by inhibiting the virus proteases.

A comparative pan-genomic analysis of 53 C. pseudotuberculosis strains based on functional domains.

Corynebacterium pseudotuberculosis is a pathogenic bacterium with great veterinary and economic importance. It is classified into two biovars: ovis, nitrate-negative, that causes lymphadenitis in small ruminants and equi, nitrate-positive, causing ulcerative lymphangitis in equines. With the explosive growth of available genomes of several strains, pan-genome analysis has opened new opportunities for understanding the dynamics and evolution of C. pseudotuberculosis. However, few pan-genomic studies have compared biovars equi and ovis. Such studies have considered a reduced number of strains and compared entire genomes. Here we conducted an original pan-genome analysis based on protein sequences and their functional domains. We considered 53 C. pseudotuberculosis strains from both biovars isolated from different hosts and countries. We have analysed conserved domains, common domains more frequently found in each biovar and biovar-specific (unique) domains. Our results demonstrated that biovar equi is more variable; there is a significant difference in the number of proteins per strains, probably indicating the occurrence of more gene loss/gain events. Moreover, strains of biovar equi presented a higher number of biovar-specific domains, 77 against only eight in biovar ovis, most of them are associated with virulence mechanisms. With this domain analysis, we have identified functional differences among strains of biovars ovis and equi that could be related to niche-adaptation and probably help to better understanding mechanisms of virulence and pathogenesis. The distribution patterns of functional domains identified in this work might have impacts on bacterial physiology and lifestyle, encouraging the development of new diagnoses, vaccines, and treatments for C. pseudotuberculosis diseases.Communicated by Ramaswamy H. Sarma.

A Computer-Aided Approach for the Discovery of D-Peptides as Inhibitors of SARS-CoV-2 Main Protease.

The SARS-CoV-2 main protease, also known as 3-chymotrypsin-like protease (3CLpro), is a cysteine protease responsible for the cleavage of viral polyproteins pp1a and pp1ab, at least, at eleven conserved sites, which leads to the formation of mature nonstructural proteins essential for the replication of the virus. Due to its essential role, numerous studies have been conducted so far, which have confirmed 3CLpro as an attractive drug target to combat Covid-19 and have reported a vast number of inhibitors and their co-crystal structures. Despite all the ongoing efforts, D-peptides, which possess key advantages over L-peptides as therapeutic agents, have not been explored as potential drug candidates against 3CLpro. The current work fills this gap by reporting an in silico approach for the discovery of D-peptides capable of inhibiting 3CLpro that involves structure-based virtual screening (SBVS) of an in-house library of D-tripeptides and D-tetrapeptides into the protease active site and subsequent rescoring steps, including Molecular Mechanics Generalized-Born Surface Area (MM-GBSA) free energy calculations and molecular dynamics (MD) simulations. In vitro enzymatic assays conducted for the four top-scoring D-tetrapeptides at 20 µM showed that all of them caused 55-85% inhibition of 3CLpro activity, thus highlighting the suitability of the devised approach. Overall, our results present a promising computational strategy to identify D-peptides capable of inhibiting 3CLpro, with broader application in problems involving protein inhibition.

Binding studies of a putative C. pseudotuberculosis target protein from Vitamin B12 Metabolism.

Vitamin B12 acts as a cofactor for various metabolic reactions important in living organisms. The Vitamin B12 biosynthesis is restricted to prokaryotes, which means, all eukaryotic organisms must acquire this molecule through diet. This study presents the investigation of Vitamin B12 metabolism and the characterization of precorrin-4 C(11)-methyltransferase (CobM), an enzyme involved in the biosynthesis of Vitamin B12 in Corynebacterium pseudotuberculosis. The analysis of the C. pseudotuberculosis genome identified two Vitamin B12-dependent pathways, which can be strongly affected by a disrupted vitamin metabolism. Molecular dynamics, circular dichroism, and NMR-STD experiments identified regions in CobM that undergo conformational changes after s-adenosyl-L-methionine binding to promote the interaction of precorrin-4, a Vitamin B12 precursor. The binding of s-adenosyl-L-methionine was examined along with the competitive binding of adenine, dATP, and suramin. Based on fluorescence spectroscopy experiments the dissociation constant for the four ligands and the target protein could be determined; SAM (1.4 ± 0.7 µM), adenine (17.8 ± 1.5 µM), dATP (15.8 ± 2.0 µM), and Suramin (6.3 ± 1.1 µM). The results provide rich information for future investigations of potential drug targets within the C. pseudotuberculosis's Vitamin B12 metabolism and related pathways to reduce the pathogen's virulence in its hosts.

The polyanions heparin and suramin impede binding of free adenine to a DNA glycosylase from C. pseudotuberculosis.

Currently no effective treatment is available to combat infections caused by Corynebacterium pseudotuberculosis in livestock. Survival of this Gram-positive bacterium in rapidly-growing pathogens in hostile environments is strongly dependent on the existence of a robust DNA repair system to prevent DNA mutations and contribute to bacterial colonization and virulence. The adenine/guanine-specific DNA glycosylase (MutY) is evolutionarily conserved and has been well characterized due to its central role in the prevention of mutagenesis and DNA repair. The aim of this study was the characterization of the target protein interaction with free adenine, suramin, and heparin, as well as the binding competition characterization between the molecules. The dissociation constant for free adenine interaction with Corynebacterium pseudotuberculosis MutY (Cp-MutY) was determined, 86 ±â€¯2.5 µM. NMR competition experiments demonstrated, that the polyanions heparin and suramin compete with adenine for the protein active site. The determined dissociation constant for the heparin/Cp-MutY interaction was 5.9 ±â€¯1.0 µM and for suramin was 16 ±â€¯1.5 µM. Docking of both polyanions with Cp-MutY revealed a possible mode of interaction and indicates that these molecules can interfere with the protein interaction with damaged DNA or prevent the binding of the adenine base in the enzyme active site.

Inhibition of thioredoxin A1 from Corynebacterium pseudotuberculosis by polyanions and flavonoids.

In pathogens, the thioredoxin system forms part of the defense against oxidative stress and ensures the formation of the proper disulfide bonds to ensure protein function. In Corynebacterium pseudotuberculosis, the role and mechanism of TrxA1 has not been elucidated, but, the significant homology among different Trxs and the conservation of the residues that form their active sites underline the importance of the Trx systems. Proteins involved in redox metabolism and low molecular weight thiols, which might interact with them, become attractive targets to modulate the activity of pathogens. The activity of the protein was investigated using a turbidimetric assay system. The influence of different pH and low molecular weight thiols were tested. Additionally, this assay was used to investigate the inhibitory potential of ligands from different molecular families, such as, polyanions (suramin and heparin) and flavonoids (hesperetin and hesperidin). All four compounds showed inhibition of the protein activity by approximately 80%. The interactions between these compounds and Cp-TrxA1 were investigated using CD spectroscopy, NMR, molecular docking and dynamics. Our results demonstrate that suramin and hesperetin can serve as lead molecules for the development of specific inhibitors for the C. pseudotuberculosis TrxA1.

Biochemical and biophysical characterization of a mycoredoxin protein glutaredoxin A1 from Corynebacterium pseudotuberculosis.

Glutaredoxin A1 from Corynebacterium pseudotuberculosis was shown to be a mycoredoxin protein. In this study, we established a process to overexpress and purify glutaredoxin A1. The aim of this study was the investigation of the Glutaredoxin A1 from C. pseudotuberculosis behavior under different redox environments and the identification of lead molecules, which can be used for specific inhibitor development for this protein family. A quantitative assay was performed measuring the rate of insulin reduction spectrophotometrically at 640nm through turbidity formation from the precipitation of the free insulin. Glutaredoxin A1, at 5µM concentration, accelerated the reduction process of 0.2mM insulin and 1mM DTT. The pH optimum of the reaction was 7.4. In the presence of DTT and ESH the glutaredoxin A1 presents similar activity, and its activity is reduced by 50% in the presence of GSH. Additional function for ESH in the redox metabolism of C. pseudotuberculosis is suggested. A combined STD and Chemical Shift - NMR approach was employed to study the effects of potential inhibitors on the structure of glutaredoxin A1 from Corynebacterium pseudotuberculosis. The inhibitory potential of four ligands (heparin, suramin, hesperetin - Hst, and hesperidin - Hsp) against glutaredoxin A1 is discussed.

Structure and interaction of Corynebacterium pseudotuberculosis cold shock protein A with Y-box single-stranded DNA fragment.

Cold shock proteins (Csps) function to preserve cell viability at low temperatures by binding to nucleic acids and consequently control gene expression. The mesophilic bacterium Corynebacterium pseudotuberculosis is the causative agent of caseous lymphadenitis in animals, and infection in livestock is a considerable economic burden worldwide. In this report, the structure of cold shock protein A from Cp (Cp-CspA) and biochemical analysis of its temperature-dependent interaction with a Y-box ssDNA motif is presented. The Cp-CspA structure contains five ß-strands making up a ß-barrel fold with 11 hydrophobic core residues and two salt bridges that confers it with a melting temperature of ~ 54 °C that is similar to mesophilic Bs-CspB. Chemical shift perturbations analysis revealed that residues in the nucleic acid-binding motifs (RNP 1 and 2) and loop 3 are involved in binding to the Y-box fragment either by direct interaction or by conformational rearrangements remote from the binding region. Fluorescence quenching experiments of Cp-CspA showed that the dissociation constants for Y-box ssDNA binding is nanomolar and the binding affinity decreased as the temperature increased, indicating that the interaction is enthalpically driven and the hydrogen bonds and van der Waals forces are important contributions for complex stabilization. The Y31 of Cp-CspA is a particular occurrence among Csps from mesophilic bacteria that provide a possible explanation for the higher binding affinity to ssDNA than that observed for Bs-CspB. Anisotropy measurements indicated that the reduction in molecular mobility of Cp-CspA upon Y-box binding is characterized by a cooperative process. DATABASE: Resonance assignment and structural data are available in the Biological Magnetic Resonance Data Bank and Protein Data Bank under accession number 26802 and 5O6F, respectively.

Cold Shock Protein A from Corynebacterium pseudotuberculosis: Role of Electrostatic Forces in the Stability of the Secondary Structure.

The conformational stability of the Cold shock protein A (CspA) from C. pseudotuberculosis (Cp), a nucleic acid binding protein in function of pH and salt concentration was examined by using differential scanning calorimetry and CD spectroscopy in combination with computational analysis to identify the specify amino acids undergoing change. Our approach identified a sodiumbinding site in CpCspA and at pH 8.0 a significant reduction in the ß-sheet content was observed which resulted in a decrease of the protein thermal stability. The computational analyses identified His30 and His65 as the amino acids with the largest charge shifts at different pHs. His30/His65 are part of the extensive hydrogen bonding network and along with the ion-binding site are essential for the conformational stability of CspA.