scholarly journals Two single-point mutations shift the ligand selectivity of a pheromone receptor between two closely related moth species

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Ke Yang ◽  
Ling-Qiao Huang ◽  
Chao Ning ◽  
Chen-Zhu Wang
Keyword(s):  
Amino Acid ◽  
Single Point ◽  
Point Mutations ◽  
Functional Difference ◽  
Amino Acid Residues ◽  
Helicoverpa Assulta ◽  
Ligand Selectivity ◽  
Olfactory Systems ◽  
Moth Species ◽  
Species Specific

Male moths possess highly sensitive and selective olfactory systems that detect sex pheromones produced by their females. Pheromone receptors (PRs) play a key role in this process. The PR HassOr14b is found to be tuned to (Z)−9-hexadecenal, the major sex-pheromone component, in Helicoverpa assulta. HassOr14b is co-localized with HassOr6 or HassOr16 in two olfactory sensory neurons within the same sensilla. As HarmOr14b, the ortholog of HassOr14b in the closely related species Helicoverpa armigera, is tuned to another chemical (Z)−9-tetradecenal, we study the amino acid residues that determine their ligand selectivity. Two amino acids located in the transmembrane domains F232I and T355I together determine the functional difference between the two orthologs. We conclude that species-specific changes in the tuning specificity of the PRs in the two Helicoverpa moth species could be achieved with just a few amino acid substitutions, which provides new insights into the evolution of closely related moth species.

scholarly journals Uncoupling of the apyrimidinic/apurinic endonucleolytic and 3′→5′ exonucleolytic activities of the Nfo protein of Mycoplasma pneumoniae through mutation of specific amino acid residues

Microbiology ◽  
2014 ◽  
Vol 160 (6) ◽  
pp. 1087-1100 ◽  
Author(s):  
Silvia Estevão ◽  
Pieternella E. van der Spek ◽  
Annemarie M. C. van Rossum ◽  
Cornelis Vink
Keyword(s):  
Mycoplasma Pneumoniae ◽  
Divalent Cations ◽  
Single Point ◽  
Dna Recombination ◽  
Point Mutations ◽  
Mycoplasma Genitalium ◽  
Amino Acid Residues ◽  
Specific Amino Acid ◽  
Cleavage Activity ◽  
Ap Sites

The DNA recombination and repair machineries of Mycoplasma pneumoniae and Mycoplasma genitalium were predicted to consist of a set of ~11 proteins. The function of one of these proteins was inferred from its homology with proteins belonging to the Endo IV enzyme family. The members of this family function in the repair of apyrimidinic/apurinic (AP) sites in DNA. As such activity may be crucial in the mycoplasmal life cycle, we set out to study the Endo IV-like proteins encoded by M. pneumoniae and M. genitalium. Both proteins, termed Nfo Mpn and Nfo Mge , respectively, were assessed for their ability to interact with damaged and undamaged DNA. In the absence of divalent cations, both proteins exhibited specific cleavage of AP sites. Surprisingly, the proteins also recognized and cleaved cholesteryl-bound deoxyribose moieties in DNA, showing that these Nfo proteins may also function in repair of large DNA adducts. In the presence of Mg2+, Nfo Mpn and Nfo Mge also showed 3′→5′ exonucleolytic activity. By introduction of 13 single point mutations at highly conserved positions within Nfo Mpn , two major types of mutants could be distinguished: (i) mutants that showed no, or limited, AP cleavage activity in the presence of EDTA, but displayed significant levels of AP cleavage activity in the presence of Mg2+; these mutants displayed no, or very low, exonucleolytic activity; and (ii) mutants that only demonstrated marginal levels of AP site cleavage activity in the presence of Mg2+ and did not show exonucleolytic activity. Together, these results indicated that the AP endonucleolytic activity of the Nfo Mpn protein can be uncoupled from its 3′→5′ exonucleolytic activity.

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

Infection ◽  
2020 ◽  
Vol 48 (6) ◽  
pp. 889-897 ◽  
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.

scholarly journals In Silico Finding of Key Interaction Mediated α3β4 and α7 Nicotinic Acetylcholine Receptor Ligand Selectivity of Quinuclidine-Triazole Chemotype

2020 ◽  
Vol 21 (17) ◽  
pp. 6189
Author(s):  
Kuntarat Arunrungvichian ◽  
Sumet Chongruchiroj ◽  
Jiradanai Sarasamkan ◽  
Gerrit Schüürmann ◽  
Peter Brust ◽  
...  
Keyword(s):  
Amino Acid ◽  
Acetylcholine Receptor ◽  
Nicotinic Acetylcholine Receptor ◽  
In Silico ◽  
Amino Acid Residues ◽  
Nicotinic Acetylcholine ◽  
Selective Binding ◽  
Ligand Selectivity ◽  
Α7 Nachr ◽  
Nachr Subtype

The selective binding of six (S)-quinuclidine-triazoles and their (R)-enantiomers to nicotinic acetylcholine receptor (nAChR) subtypes α3β4 and α7, respectively, were analyzed by in silico docking to provide the insight into the molecular basis for the observed stereospecific subtype discrimination. Homology modeling followed by molecular docking and molecular dynamics (MD) simulations revealed that unique amino acid residues in the complementary subunits of the nAChR subtypes are involved in subtype-specific selectivity profiles. In the complementary β4-subunit of the α3β4 nAChR binding pocket, non-conserved AspB173 through a salt bridge was found to be the key determinant for the α3β4 selectivity of the quinuclidine-triazole chemotype, explaining the 47–327-fold affinity of the (S)-enantiomers as compared to their (R)-enantiomer counterparts. Regarding the α7 nAChR subtype, the amino acids promoting a however significantly lower preference for the (R)-enantiomers were the conserved TyrA93, TrpA149 and TrpB55 residues. The non-conserved amino acid residue in the complementary subunit of nAChR subtypes appeared to play a significant role for the nAChR subtype-selective binding, particularly at the heteropentameric subtype, whereas the conserved amino acid residues in both principal and complementary subunits are essential for ligand potency and efficacy.

scholarly journals Activation of Ha-ras p21 by substitution, deletion, and insertion mutations.

1985 ◽  
Vol 5 (8) ◽  
pp. 1809-1813 ◽  
Author(s):  
R G Chipperfield ◽  
S S Jones ◽  
K M Lo ◽  
R A Weinberg
Keyword(s):  
Amino Acid ◽  
Point Mutations ◽  
Normal Function ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Transforming Activity ◽  
Ras P21 ◽  
Ras Oncogenes ◽  
Insertion Mutations

The transforming activity of naturally arising ras oncogenes results from point mutations that affect residue 12 or 61 of the encoded 21-kilodalton protein (p21). By use of site-directed mutagenesis, we showed that deletions and insertions of amino acid residues in the region of residue 12 are also effective in conferring oncogenic activity on p21. Common to these various alterations is the disruption that they create in this domain of the protein, which we propose results in the inactivation of a normal function of the protein.

scholarly journals Determinants of Human CD134 Essential for Entry of Human Herpesvirus 6B

2015 ◽  
Vol 89 (19) ◽  
pp. 10125-10129 ◽  
Author(s):  
Huamin Tang ◽  
Yasuko Mori
Keyword(s):  
Amino Acid ◽  
Human Herpesvirus ◽  
Amino Acid Residues ◽  
Ligand Interaction ◽  
Receptor Ligand ◽  
Species Specific

We identified two key amino acid residues within human CD134 (hCD134) that are required for its interaction with human herpesvirus 6B (HHV-6B) and for HHV-6B entry into cells. One of the residues (K79) allows access of the HHV-6B ligand to hCD134. Murine CD134 (mCD134) functioned as an HHV-6B receptor when these two amino acid residues were replaced with homologous human residues. This study identifies both the HHV-6B receptor-ligand interaction and the species-specific determinants of hCD134 essential for HHV-6B entry.

scholarly journals Molecular Genetic Analysis of Revertants from a Poliovirus Mutant That Is Specifically Adapted to the Mouse Spinal Cord

2001 ◽  
Vol 75 (23) ◽  
pp. 11766-11772 ◽  
Author(s):  
Qingmei Jia ◽  
James M. Hogle ◽  
Tsutomu Hashikawa ◽  
Akio Nomoto
Keyword(s):  
Amino Acid ◽  
Genetic Analysis ◽  
Single Point ◽  
Molecular Genetic ◽  
Molecular Genetic Analysis ◽  
Amino Acid Residues ◽  
Site Mutation ◽  
Mutation Site ◽  
Large Plaque ◽  
Inoculation Route

ABSTRACT SA virus, a mutant of the Mahoney strain of type 1 poliovirus (PV1/Mahoney), replicates specifically in the spinal cords of mice and causes paralysis, although the PV1/Mahoney strain does not show any mouse neurovirulence (Q. Jia, S. Ohka, K. Iwasaki, K. Tohyama, and A. Nomoto, J. Virol. 73:6041–6047, 1999). The key mutation site for the mouse neurovirulence of SA was mapped to nucleotide (nt) 928 of the genome (A to G), resulting in the amino acid substitution of Met for Ile at residue 62 within the capsid protein VP4 (VP4062). A small-plaque phenotype of SA appears to be indicative of its mouse-neurovirulent phenotype. To identify additional amino acid residues involved in the host range determination of PV, a total of 14 large-plaque (LP) variants were isolated from a single point mutant, Mah/I4062M, that showed the SA phenotype. All the LP variants no longer showed any mouse neurovirulence when delivered via an intraspinal inoculation route. Of these, 11 isolates had a back mutation at nt 928 (G to A) that restored the nucleotide of the PV1/Mahoney type. The reversions of the remaining three isolates (LP8, LP9, and LP14) were mediated by a second site mutation. Molecular genetic analysis involving recombinants between Mah/I4062M and the LP variants revealed that the mere substitution of an amino acid residue at position 107 in VP1 (Val to Leu) (LP9), position 33 in VP2 (Val to Ile) (LP14), or position 231 in VP3 (Ile to Thr) (LP8) was sufficient to restore the PV1/Mahoney phenotype. These amino acid residues are located either on the surface or inside of the virus particle. Our results indicate that the mouse neurovirulence of PV is determined by the virion surface structure, which is formed by all four capsid proteins.

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