scholarly journals New self-identities evolve via point mutation in an invertebrate allorecognition gene

2020 ◽  
Author(s):  
Aidan Huene ◽  
Traci Chen ◽  
Matthew L. Nicotra
Keyword(s):  
Amino Acid ◽  
Point Mutation ◽  
Direct Evidence ◽  
Transmembrane Protein ◽  
Amino Acid Substitutions ◽  
Functional Variation ◽  
Hydractinia Symbiolongicarpus ◽  
Self Recognition ◽  
Two Component ◽  
Recognition Systems

SummaryMany organisms use genetic self-recognition systems to distinguish themselves from other members of their species. To understand how new self-identities evolve, we studied Allorecognition 2 (Alr2), a self-recognition gene from the colonial cnidarian, Hydractinia symbiolongicarpus. Alr2 encodes a highly polymorphic transmembrane protein that discriminates self from non-self by selectively binding across cell membranes to other Alr2 proteins with identical or very similar sequences. Here, we show that new Alr2 proteins evolve by amino acid substitutions that immediately create isoforms with entirely novel binding specificities, or through intermediates with relaxed binding specificities. Our results also suggest a topology for homophilic interactions between Alr2 proteins. These results provide direct evidence for the generation and maintenance of functional variation at an allorecognition locus and reveal that one-component and two-component self-recognition systems evolve via different mechanisms.

scholarly journals Substrate Range and Genetic Analysis ofAcinetobacter Vanillate Demethylase

2000 ◽  
Vol 182 (5) ◽  
pp. 1383-1389 ◽  
Author(s):  
Birgit Morawski ◽  
Ana Segura ◽  
L. Nicholas Ornston
Keyword(s):  
Amino Acid ◽  
Amino Acid Substitutions ◽  
Missense Mutations ◽  
Amino Acid Residues ◽  
Wild Type ◽  
Nucleotide Substitutions ◽  
Two Component ◽  
Selection For ◽  
Type Sequence ◽  
Selection Of

ABSTRACT An Acinetobacter sp. genetic screen was used to probe structure-function relationships in vanillate demethylase, a two-component monooxygenase. Mutants with null, leaky, and heat-sensitive phenotypes were isolated. Missense mutations tended to be clustered in specific regions, most of which make known contributions to catalytic activity. The vanillate analogsm-anisate, m-toluate, and 4-hydroxy-3,5-dimethylbenzoate are substrates of the enzyme and weakly inhibit the metabolism of vanillate by wild-typeAcinetobacter bacteria. PCR mutagenesis ofvanAB, followed by selection for strains unable to metabolize vanillate, yielded mutant organisms in which vanillate metabolism is more strongly inhibited by the vanillate analogs. Thus, the procedure opens for investigation amino acid residues that may contribute to the binding of either vanillate or its chemical analogs to wild-type and mutant vanillate demethylases. Selection of phenotypic revertants following PCR mutagenesis gave an indication of the extent to which amino acid substitutions can be tolerated at specified positions. In some cases, only true reversion to the original amino acid was observed. In other examples, a range of amino acid substitutions was tolerated. In one instance, phenotypic reversion failed to produce a protein with the original wild-type sequence. In this example, constraints favoring certain nucleotide substitutions appear to be imposed at the DNA level.

scholarly journals Alterations in Two-Component Regulatory Systems of phoPQ and pmrAB Are Associated with Polymyxin B Resistance in Clinical Isolates of Pseudomonas aeruginosa

2009 ◽  
Vol 53 (12) ◽  
pp. 5150-5154 ◽  
Author(s):  
Kaddy Barrow ◽  
Dong H. Kwon
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Amino Acid ◽  
Polymyxin B ◽  
Clinical Isolates ◽  
Single Amino Acid ◽  
Amino Acid Substitutions ◽  
Strain Pao1 ◽  
Truncated Protein ◽  
Regulatory Systems ◽  
Two Component

ABSTRACT Polymyxins are often the only option to treat acquired multidrug-resistant Pseudomonas aeruginosa. Polymyxin susceptibility in P. aeruginosa PAO1 is associated with the lipopolysaccharide structure that is determined by arnBCADTEF and modulated by phoPQ and pmrAB. We examined five clonally unrelated clinical isolates of polymyxin B-resistant P. aeruginosa to investigate the molecular basis of polymyxin resistance. All isolates grew with 4 μg/ml polymyxin B (MIC, 8 μg/ml), whereas P. aeruginosa PAO1 grew with 0.25 μg/ml polymyxin B (MIC, 0.5 μg/ml). The resistant isolates were converted to susceptible ones (the MICs fell from 8 to 0.5 μg/ml) following the introduction of phoPQ (four isolates) and pmrAB (one isolate), which had been cloned from strain PAO1. DNA sequence analysis revealed that a single-nucleotide substitution in three isolates replaced a single amino acid of PhoQ, the deletion of 17 nucleotides in one isolate truncated the protein of PhoQ, and two nucleotide substitutions in one isolate replaced two amino acids of PmrB. The involvement of these amino acid substitutions or the truncated protein of PhoQ and PmrB in polymyxin B resistance was confirmed using strain PAO1 lacking phoPQ or pmrAB that was transformed by phoPQ or pmrAB containing the amino acid substitutions or the truncated protein. The resistant clinical isolates were sensitized by the inactivation of arnBCADTEF (the MICs fell from 8 to 0.5 μg/ml). These results suggest that polymyxin B resistance among clinical isolates of P. aeruginosa is associated with alterations in two-component regulatory systems of phoPQ or pmrAB.

scholarly journals Characterization of Amino Acid Substitutions in the Two-Component Regulatory System AdeRS Identified in Multidrug-Resistant Acinetobacter baumannii

mSphere ◽  
2021 ◽  
Author(s):  
K. Lucaßen ◽  
K. Xanthopoulou ◽  
J. Wille ◽  
T. Wille ◽  
Y. Wen ◽  
...  
Keyword(s):  
Amino Acid ◽  
Antimicrobial Resistance ◽  
Acinetobacter Baumannii ◽  
Regulatory System ◽  
Efflux Pumps ◽  
Multidrug Resistant ◽  
Amino Acid Substitutions ◽  
Active Efflux ◽  
Two Component

The active efflux of antimicrobials by bacteria can lead to antimicrobial resistance and persistence and can affect multiple different classes of antimicrobials. Efflux pumps are tightly regulated, and their overexpression can be mediated by changes in their regulators.

Recombinant Variants of Tissue-Type Plasminogen Activator Containing Amino Acid Substitutions in the Finger Domain

1992 ◽  
Vol 68 (06) ◽  
pp. 672-677 ◽  
Author(s):  
Hitoshi Yahara ◽  
Keiji Matsumoto ◽  
Hiroyuki Maruyama ◽  
Tetsuya Nagaoka ◽  
Yasuhiro Ikenaka ◽  
...  
Keyword(s):  
Amino Acid ◽  
Plasminogen Activator ◽  
Half Life ◽  
Tissue Type ◽  
Clot Lysis ◽  
Amino Acid Substitutions ◽  
Wild Type ◽  
Plasma Clot ◽  
Tissue Type Plasminogen Activator ◽  
Type Plasminogen Activator

SummaryTissue-type plasminogen activator (t-PA) is a fibrin-specific agent which has been used to treat acute myocardial infarction. In an attempt to clarify the determinants for its rapid clearance in vivo and high affinity for fibrin clots, we produced five variants containing amino acid substitutions in the finger domain, at amino acid residues 7–9, 10–14, 15–19, 28–33, and 37–42. All the variants had a prolonged half-life and a decreased affinity for fibrin of various degrees. The 37–42 variant demonstrated about a 6-fold longer half-life with a lower affinity for fibrin. Human plasma clot lysis assay estimated the fibrinolytic activity of the 37–42 variant to be 1.4-fold less effective than that of the wild-type rt-PA. In a rabbit jugular vein clot lysis model, doses of 1.0 and 0.15 mg/kg were required for about 70% lysis in the wild-type and 37–42 variant, respectively. Fibrinogen was degraded only when the wild-type rt-PA was administered at a dose of 1.0 mg/kg. These findings suggest that the 37–42 variant can be employed at a lower dosage and that it is a more fibrin-specific thrombolytic agent than the wild-type rt-PA.

Paris I Dysfibrinogenemia: A Point Mutation in Intron 8 Results in Insertion of a 15 Amino Acid Sequence in the Fibrinogen γ-Chain

1993 ◽  
Vol 69 (03) ◽  
pp. 217-220 ◽  
Author(s):  
Jonathan B Rosenberg ◽  
Peter J Newman ◽  
Michael W Mosesson ◽  
Marie-Claude Guillin ◽  
David L Amrani
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Point Mutation ◽  
Genomic Dna ◽  
Comparative Sequence Analysis ◽  
Chain Gene ◽  
Molecular Defect ◽  
Nucleotide Position ◽  
Normal Individuals ◽  
Polymerase Chain

SummaryParis I dysfibrinogenemia results in the production of a fibrinogen molecule containing a functionally abnormal γ-chain. We determined the basis of the molecular defect using polymerase chain reaction (PCR) to amplify the γ-chain region of the Paris I subject’s genomic DNA. Comparative sequence analysis of cloned PCR segments of normal and Paris I genomic DNA revealed only an A→G point mutation occurring at nucleotide position 6588 within intron 8 of the Paris I γ-chain gene. We examined six normal individuals and found only normal sequence in this region, indicating that this change is not likely to represent a normal polymorphism. This nucleotide change leads to a 45 bp fragment being inserted between exons 8 and 9 in the mature γparis I chain mRNA, and encodes a 15 amino acid insert after γ350 [M-C-G-E-A-L-P-M-L-K-D-P-C-Y]. Alternative splicing of this region from intron 8 into the mature Paris I γ-chain mRNA also results after translation into a substitution of S for G at position γ351. Biochemical studies of 14C-iodoacetamide incorporation into disulfide-reduced Paris I and normal fibrinogen corroborated the molecular biologic predictions that two additional cysteine residues exist within the γpariS I chain. We conclude that the insertion of this amino acid sequence leads to a conformationallyaltered, and dysfunctional γ-chain in Paris I fibrinogen.

Sign in / Sign up

Export Citation Format

Share Document