Tuning Structure and Dynamics of Blue Copper Azurin Junctions via Single Amino-Acid Mutations

In the growing field of biomolecular electronics, blue-copper Azurin stands out as one of the most widely studied protein in single-molecule contacts. Interestingly, despite the paramount importance of the structure/dynamics of molecular contacts in their transport properties, these factors remain largely unexplored from the theoretical point of view in the context of single Azurin junctions. Here we address this issue using all-atom Molecular Dynamics (MD) of Pseudomonas Aeruginosa Azurin adsorbed to a Au(111) substrate. In particular, we focus on the structure and dynamics of the free/adsorbed protein and how these properties are altered upon single-point mutations. The results revealed that wild-type Azurin adsorbs on Au(111) along two well defined configurations: one tethered via cysteine groups and the other via the hydrophobic pocket surrounding the Cu 2 + . Surprisingly, our simulations revealed that single amino-acid mutations gave rise to a quenching of protein vibrations ultimately resulting in its overall stiffening. Given the role of amino-acid vibrations and reorientation in the dehydration process at the protein-water-substrate interface, we suggest that this might have an effect on the adsorption process of the mutant, giving rise to new adsorption configurations.

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Free-energy changes of bacteriorhodopsin point mutants measured by single-molecule force spectroscopy

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2020083118 ◽

2021 ◽

Vol 118 (13) ◽

pp. e2020083118

Author(s):

David R. Jacobson ◽

Thomas T. Perkins

Keyword(s):

Free Energy ◽

Amino Acid ◽

Membrane Protein ◽

Single Molecule ◽

Point Mutations ◽

Single Amino Acid ◽

Chemical Denaturation ◽

Amino Acid Region ◽

Amino Acid Mutations ◽

Lipid Environment

Single amino acid mutations provide quantitative insight into the energetics that underlie the dynamics and folding of membrane proteins. Chemical denaturation is the most widely used assay and yields the change in unfolding free energy (ΔΔG). It has been applied to >80 different residues of bacteriorhodopsin (bR), a model membrane protein. However, such experiments have several key limitations: 1) a nonnative lipid environment, 2) a denatured state with significant secondary structure, 3) error introduced by extrapolation to zero denaturant, and 4) the requirement of globally reversible refolding. We overcame these limitations by reversibly unfolding local regions of an individual protein with mechanical force using an atomic-force-microscope assay optimized for 2 μs time resolution and 1 pN force stability. In this assay, bR was unfolded from its native bilayer into a well-defined, stretched state. To measure ΔΔG, we introduced two alanine point mutations into an 8-amino-acid region at the C-terminal end of bR’s G helix. For each, we reversibly unfolded and refolded this region hundreds of times while the rest of the protein remained folded. Our single-molecule–derived ΔΔG for mutant L223A (−2.3 ± 0.6 kcal/mol) quantitatively agreed with past chemical denaturation results while our ΔΔG for mutant V217A was 2.2-fold larger (−2.4 ± 0.6 kcal/mol). We attribute the latter result, in part, to contact between Val217 and a natively bound squalene lipid, highlighting the contribution of membrane protein–lipid contacts not present in chemical denaturation assays. More generally, we established a platform for determining ΔΔG for a fully folded membrane protein embedded in its native bilayer.

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Mutations in Plasmodium falciparumCytochrome b That Are Associated with Atovaquone Resistance Are Located at a Putative Drug-Binding Site

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.44.8.2100-2108.2000 ◽

2000 ◽

Vol 44 (8) ◽

pp. 2100-2108 ◽

Cited By ~ 232

Author(s):

Michael Korsinczky ◽

Nanhua Chen ◽

Barbara Kotecka ◽

Allan Saul ◽

Karl Rieckmann ◽

...

Keyword(s):

Amino Acid ◽

Binding Site ◽

Point Mutations ◽

Drug Binding ◽

Single Amino Acid ◽

Malaria Parasites ◽

Drug Binding Site ◽

Sole Agent ◽

Amino Acid Mutations

ABSTRACT Atovaquone is the major active component of the new antimalarial drug Malarone. Considerable evidence suggests that malaria parasites become resistant to atovaquone quickly if atovaquone is used as a sole agent. The mechanism by which the parasite develops resistance to atovaquone is not yet fully understood. Atovaquone has been shown to inhibit the cytochrome bc 1 (CYTbc 1) complex of the electron transport chain of malaria parasites. Here we report point mutations in Plasmodium falciparum CYT b that are associated with atovaquone resistance. Single or double amino acid mutations were detected from parasites that originated from a cloned line and survived various concentrations of atovaquone in vitro. A single amino acid mutation was detected in parasites isolated from a recrudescent patient following atovaquone treatment. These mutations are associated with a 25- to 9,354-fold range reduction in parasite susceptibility to atovaquone. Molecular modeling showed that amino acid mutations associated with atovaquone resistance are clustered around a putative atovaquone-binding site. Mutations in these positions are consistent with a reduced binding affinity of atovaquone for malaria parasite CYTb.

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Intrinsic resistance to terbinafine among human and animal isolates of Trichophyton mentagrophytes related to amino acid substitution in the squalene epoxidase

Infection ◽

10.1007/s15010-020-01498-1 ◽

2020 ◽

Vol 48 (6) ◽

pp. 889-897 ◽

Cited By ~ 1

Author(s):

Dominik Łagowski ◽

Sebastian Gnat ◽

Aneta Nowakiewicz ◽

Marcelina Osińska ◽

Mariusz Dyląg

Keyword(s):

Amino Acid ◽

Fungal Infections ◽

Single Point ◽

Antifungal Susceptibility ◽

Point Mutations ◽

Trichophyton Mentagrophytes ◽

Single Amino Acid ◽

Squalene Epoxidase ◽

Intrinsic Resistance ◽

Resistant Strains

Abstract Background Dermatomycoses are the most common fungal infections in the world affecting a significant part of the human and animal population. The majority of zoophilic infections in humans are caused by Trichophyton mentagrophytes. Currently, the first-line drug for both oral and topical therapy is terbinafine. However, an increasing number of cases that are difficult to be cured with this drug have been noted in Europe and Asia. Resistance to terbinafine and other allylamines is very rare and usually correlated with point mutations in the squalene epoxidase gene resulting in single amino acid substitutions in the enzyme, which is crucial in the ergosterol synthesis pathway. Purpose Here, we report terbinafine-resistant T. mentagrophytes isolates among which one was an etiological factor of tinea capitis in a man and three were obtained from asymptomatic foxes in Poland. Methods We used the CLSI protocol to determine antifungal susceptibility profiles of naftifine, amphotericin B, griseofulvin, ketoconazole, miconazole, itraconazole, voriconazole, and ciclopirox. Moreover, the squalene epoxidase gene of the terbinafine-resistant strains was sequenced and analysed. Results In the genomes of all four resistant strains exhibiting elevated MICs to terbinafine (16 to 32 µg/ml), single-point mutations leading to Leu393Phe substitution in the squalene epoxidase enzyme were revealed. Among the other tested substances, a MIC50 value of 1 µg/ml was shown only for griseofulvin. Conclusion Finally, our study revealed that the terbinafine resistance phenomenon might not be acquired by exposure to the drug but can be intrinsic. This is evidenced by the description of the terbinafine-resistant strains isolated from the asymptomatic animals.

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Visualizing Deep Mutational Scan Data

10.1101/418525 ◽

2018 ◽

Author(s):

C. K. Sruthi ◽

Hemalatha Balaram ◽

Meher K. Prakash

Keyword(s):

Amino Acid ◽

Single Point ◽

Point Mutations ◽

Random Mutagenesis ◽

Opportunity To Learn ◽

Single Point Mutations ◽

The Rich ◽

Amino Acid Mutations ◽

Rich Data ◽

And Function

AbstractSite-directed and random mutagenesis are biochemical tools to obtain insights into the structure and function of proteins. Recent advances such as deep mutational scan have allowed a complete scan of all the amino acid positions in a protein with each of the 19 possible alternatives. Mapping out the phenotypic consequences of thousands of single point mutations in the same protein is now possible. Visualizing and analysing the rich data offers an opportunity to learn more about the effects of mutations, for a better understanding and engineering of proteins. This work focuses on such visualization analyses applied to the mutational data of TEM-1 β-lactamase. The data is examined in the light of the expected biochemical effects of single point mutations, with the goal of reinforcing or retraining the intuitions. Individual attributes of the amino acid mutations such as the solvent accessible area, charge type change, and distance from the catalytic center capture most of the relevant functional effects. Visualizing the data suggests how combinations of these attributes can be used for a better classification of the effects of mutations, when independently they do not offer a high predictability.

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A single lysine in the N-terminal region of store-operated channels is critical for STIM1-mediated gating

The Journal of General Physiology ◽

10.1085/jgp.201010484 ◽

2010 ◽

Vol 136 (6) ◽

pp. 673-686 ◽

Cited By ~ 67

Author(s):

Annette Lis ◽

Susanna Zierler ◽

Christine Peinelt ◽

Andrea Fleig ◽

Reinhold Penner

Keyword(s):

Plasma Membrane ◽

Amino Acid ◽

Calcium Release ◽

Transmembrane Domain ◽

Single Point ◽

Point Mutations ◽

Terminal Region ◽

Single Amino Acid ◽

Critical Element ◽

Crac Channels

Store-operated Ca2+ entry is controlled by the interaction of stromal interaction molecules (STIMs) acting as endoplasmic reticulum ER Ca2+ sensors with calcium release–activated calcium (CRAC) channels (CRACM1/2/3 or Orai1/2/3) in the plasma membrane. Here, we report structural requirements of STIM1-mediated activation of CRACM1 and CRACM3 using truncations, point mutations, and CRACM1/CRACM3 chimeras. In accordance with previous studies, truncating the N-terminal region of CRACM1 or CRACM3 revealed a 20–amino acid stretch close to the plasma membrane important for channel gating. Exchanging the N-terminal region of CRACM3 with that of CRACM1 (CRACM3-N(M1)) results in accelerated kinetics and enhanced current amplitudes. Conversely, transplanting the N-terminal region of CRACM3 into CRACM1 (CRACM1-N(M3)) leads to severely reduced store-operated currents. Highly conserved amino acids (K85 in CRACM1 and K60 in CRACM3) in the N-terminal region close to the first transmembrane domain are crucial for STIM1-dependent gating of CRAC channels. Single-point mutations of this residue (K85E and K60E) eliminate store-operated currents induced by inositol 1,4,5-trisphosphate and reduce store-independent gating by 2-aminoethoxydiphenyl borate. However, short fragments of these mutant channels are still able to communicate with the CRAC-activating domain of STIM1. Collectively, these findings identify a single amino acid in the N terminus of CRAC channels as a critical element for store-operated gating of CRAC channels.

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Terbinafine Resistance of Trichophyton Clinical Isolates Caused by Specific Point Mutations in the Squalene Epoxidase Gene

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00115-17 ◽

2017 ◽

Vol 61 (7) ◽

Cited By ~ 80

Author(s):

Tsuyoshi Yamada ◽

Mari Maeda ◽

Mohamed Mahdi Alshahni ◽

Reiko Tanaka ◽

Takashi Yaguchi ◽

...

Keyword(s):

Amino Acid ◽

Single Point ◽

Point Mutations ◽

Trichophyton Mentagrophytes ◽

Antifungal Drugs ◽

Clinical Isolates ◽

Single Amino Acid ◽

Squalene Epoxidase ◽

Amino Acid Substitutions ◽

Content Type

ABSTRACT Terbinafine is one of the allylamine antifungal agents whose target is squalene epoxidase (SQLE). This agent has been extensively used in the therapy of dermatophyte infections. The incidence of patients with tinea pedis or unguium tolerant to terbinafine treatment prompted us to screen the terbinafine resistance of all Trichophyton clinical isolates from the laboratory of the Centre Hospitalier Universitaire Vaudois collected over a 3-year period and to identify their mechanism of resistance. Among 2,056 tested isolates, 17 (≈1%) showed reduced terbinafine susceptibility, and all of these were found to harbor SQLE gene alleles with different single point mutations, leading to single amino acid substitutions at one of four positions (Leu393, Phe397, Phe415, and His440) of the SQLE protein. Point mutations leading to the corresponding amino acid substitutions were introduced into the endogenous SQLE gene of a terbinafine-sensitive Arthroderma vanbreuseghemii (formerly Trichophyton mentagrophytes) strain. All of the generated A. vanbreuseghemii transformants expressing mutated SQLE proteins exhibited obvious terbinafine-resistant phenotypes compared to the phenotypes of the parent strain and of transformants expressing wild-type SQLE proteins. Nearly identical phenotypes were also observed in A. vanbreuseghemii transformants expressing mutant forms of Trichophyton rubrum SQLE proteins. Considering that the genome size of dermatophytes is about 22 Mb, the frequency of terbinafine-resistant clinical isolates was strikingly high. Increased exposure to antifungal drugs could favor the generation of resistant strains.

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Genetic Variation and Evolution of the 2019 Novel Coronavirus

Public Health Genomics ◽

10.1159/000513530 ◽

2021 ◽

pp. 1-13

Author(s):

Salvatore Dimonte ◽

Muhammed Babakir-Mina ◽

Taib Hama-Soor ◽

Salar Ali

Keyword(s):

Amino Acid ◽

Receptor Binding ◽

Rapid Evolution ◽

Single Amino Acid ◽

Angiotensin Converting Enzyme 2 ◽

New Type ◽

Amino Acid Mutations ◽

Host Infection ◽

Human Coronaviruses ◽

Novel Coronavirus

Introduction: SARS-CoV-2 is a new type of coronavirus causing a pandemic severe acute respiratory syndrome (SARS-2). Coronaviruses are very diverting genetically and mutate so often periodically. The natural selection of viral mutations may cause host infection selectivity and infectivity. Methods: This study was aimed to indicate the diversity between human and animal coronaviruses through finding the rate of mutation in each of the spike, nucleocapsid, envelope, and membrane proteins. Results: The mutation rate is abundant in all 4 structural proteins. The most number of statistically significant amino acid mutations were found in spike receptor-binding domain (RBD) which may be because it is responsible for a corresponding receptor binding in a broad range of hosts and host selectivity to infect. Among 17 previously known amino acids which are important for binding of spike to angiotensin-converting enzyme 2 (ACE2) receptor, all of them are conservative among human coronaviruses, but only 3 of them significantly are mutated in animal coronaviruses. A single amino acid aspartate-454, that causes dissociation of the RBD of the spike and ACE2, and F486 which gives the strength of binding with ACE2 remain intact in all coronaviruses. Discussion/Conclusion: Observations of this study provided evidence of the genetic diversity and rapid evolution of SARS-CoV-2 as well as other human and animal coronaviruses.

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A Single Point Mutation, Asn16→Lys, Dictates the Temperature-Sensitivity of the Reovirus tsG453 Mutant

Viruses ◽

10.3390/v13020289 ◽

2021 ◽

Vol 13 (2) ◽

pp. 289

Author(s):

Kathleen K. M. Glover ◽

Danica M. Sutherland ◽

Terence S. Dermody ◽

Kevin M. Coombs

Keyword(s):

Amino Acid ◽

Temperature Sensitivity ◽

Reverse Genetics ◽

Core Protein ◽

Single Point ◽

Single Amino Acid ◽

Single Point Mutation ◽

Temperature Sensitive ◽

Amino Acid Substitutions ◽

Gene Encoding

Studies of conditionally lethal mutants can help delineate the structure-function relationships of biomolecules. Temperature-sensitive (ts) mammalian reovirus (MRV) mutants were isolated and characterized many years ago. Two of the most well-defined MRV ts mutants are tsC447, which contains mutations in the S2 gene encoding viral core protein σ2, and tsG453, which contains mutations in the S4 gene encoding major outer-capsid protein σ3. Because many MRV ts mutants, including both tsC447 and tsG453, encode multiple amino acid substitutions, the specific amino acid substitutions responsible for the ts phenotype are unknown. We used reverse genetics to recover recombinant reoviruses containing the single amino acid polymorphisms present in ts mutants tsC447 and tsG453 and assessed the recombinant viruses for temperature-sensitivity by efficiency-of-plating assays. Of the three amino acid substitutions in the tsG453 S4 gene, Asn16-Lys was solely responsible for the tsG453ts phenotype. Additionally, the mutant tsC447 Ala188-Val mutation did not induce a temperature-sensitive phenotype. This study is the first to employ reverse genetics to identify the dominant amino acid substitutions responsible for the tsC447 and tsG453 mutations and relate these substitutions to respective phenotypes. Further studies of other MRV ts mutants are warranted to define the sequence polymorphisms responsible for temperature sensitivity.

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Characterization of an enhanced antigenic change in the pandemic 2009 H1N1 influenza virus haemagglutinin

Journal of General Virology ◽

10.1099/vir.0.061598-0 ◽

2014 ◽

Vol 95 (5) ◽

pp. 1033-1042 ◽

Cited By ~ 5

Author(s):

Blanca García-Barreno ◽

Teresa Delgado ◽

Sonia Benito ◽

Inmaculada Casas ◽

Francisco Pozo ◽

...

Keyword(s):

Influenza Virus ◽

Amino Acid ◽

Influenza A ◽

Point Mutations ◽

Antigenic Site ◽

Single Amino Acid ◽

Antigenic Structure ◽

Human Antibody ◽

2009 H1n1

Murine hybridomas producing neutralizing mAbs specific to the pandemic influenza virus A/California/07/2009 haemagglutinin (HA) were isolated. These antibodies recognized at least two different but overlapping new epitopes that were conserved in the HA of most Spanish pandemic isolates. However, one of these isolates (A/Extremadura/RR6530/2010) lacked reactivity with the mAbs and carried two unique mutations in the HA head (S88Y and K136N) that were required simultaneously to eliminate reactivity with the murine antibodies. This unusual requirement directly illustrates the phenomenon of enhanced antigenic change proposed previously for the accumulation of simultaneous amino acid substitutions at antigenic sites of the influenza A virus HA during virus evolution (Shih et al., Proc Natl Acad Sci USA, 104 , 6283–6288, 2007). The changes found in the A/Extremadura/RR6530/2010 HA were not found in escape mutants selected in vitro with one of the mAbs, which contained instead nearby single amino acid changes in the HA head. Thus, either single or double point mutations may similarly alter epitopes of the new antigenic site identified in this work in the 2009 H1N1 pandemic virus HA. Moreover, this site is relevant for the human antibody response, as shown by competition of mAbs and human post-infection sera for virus binding. The results are discussed in the context of the HA antigenic structure and challenges posed for identification of sequence changes with possible antigenic impact during virus surveillance.

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