Variation and predicted structure of the flagellin gene in Actinoplanes species.

Members of the genus Actinoplanes are considered to be representative of motile actinomycetes. To infer the flagellar diversity of Actinoplanes species, novel degenerate primers were designed for the flagellin (fliC) gene. The fliC gene of 21 Actinoplanes strains was successfully amplified and classified into two groups based on whether they were large (type I) or small (type II). Comparison of the translated amino acid sequences revealed that this size difference could be attributed to large number of gaps located in the central variable region. However, the C- and N- terminal regions were conserved. Except for a region on the flagellum surface, structural predictions of type I and II flagellins revealed that the two flagellin types were strongly correlated with each other. Phylogenetic analysis of the 115-amino acid N-terminal sequences revealed that the Actinoplanes species formed three clusters, and type II flagellin gene containing three type strains were phylogenetically closely related each other.