Selection for functional diversity drives accumulation of point mutations in Dr adhesins of Escherichia coli.

摘要: Immune escape is considered to be the driving force behind structural variability of major antigens on surface bacterial pathogens, such as fimbriae. In Dr family Escherichia coli adhesins, and adhesive functions are carried out by same subunit. adhesins have been shown bind decay-accelerating factor (DAF), collagen IV, carcinoembryonic antigen-related cell adhesion molecules (CEACAMs). We show that genes encoding from 100 E. strains form eight groups with a high level amino acid sequence diversity between them. However, comprising each group differ other only small number point mutations. Out 66 polymorphisms identified within groups, three were synonymous mutations, indicating strong positive selection for replacements. Functional analysis intragroup variants haemagglutinin (DraE) revealed mutations result in distinctly different binding phenotypes, tendency increased affinity DAF, decreased sensitivity DAF inhibition chloramphenicol, loss capability collagen, CEACAM3 CEACAM6. Thus, mutation antigenic proteins can signature functional modification.