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Structural and functional implications of sequence diversity of Pseudomonas aeruginosa genes oriC, ampC and fliC
Author(s) -
Spangenberg Claudia,
Montie Thomas C.,
Tümmler Burkhard
Publication year - 1998
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.1150190414
Subject(s) - biology , genetics , gene , nonsynonymous substitution , dnaa , sequence analysis , sequence alignment , plasmid , nucleic acid sequence , peptide sequence , genome , origin of replication
Sequence analysis of three representative gene loci, oriC, ampC and fliC , in 19 Pseudomonas aeruginosa strains revealed a low sequence diversity that does not correlate with the extensive diversity of P. aeruginosa habitats. Single point mutations lead to a mean sequence diversity of 0.40%, 0.38% and 0.59% for oriC, ampC and a‐type fliC , respectively, but of only 0.05% for b‐type flagellin genes. The analyzed genes encode highly conserved functions that are subject to strong selective pressure. The detected nucleotide substitutions of oriC , accumulating in a central 95 bp region, affect neither the putative DnaA binding sites nor the 13 bp direct repeats that presumably provide the sites to open oriC duplex DNA. Even in P. aeruginosa strain DSM 1128, which exhibits an unusually high sequence variability in several analyzed genes, the 9 bp and 13 bp motifs are conserved, reflecting their essential functional role in replication initiation. The two flagellin types, differing by 37–38% in their primary structure, exhibit pronounced structural and functional homology, as shown by alignment of flagellin variants by hydrophobicity index, probability of surface exposure, chain flexibility and antigenicity, and by cross‐reactivity between both proteins using specific antisera. Five nonsynonymous nucleotide substitutions of ampC lead to β‐lactamase variants that differ in recognition and turnover of substrate, as deduced from the three‐dimensional structure of the highly homologous Enterobacter cloacae β‐lactamase and confirmed by inhibition kinetics. The identified point mutations in the three genes are classified as selectively equivalent sequence variants indicating neutral genetic drift as a mechanism of molecular evolution in P. aeruginosa , rather than positive selection.