Identification of proteins of the outer (L and P) rings of the flagellar basal body of Escherichia coli.

Synthesis of the Salmonella typhimurium hook protein from the gene cloned on a multicopy plasmid results in partial suppression of the flagellar assembly defects of certain classes of Escherichia coli mutants (K. Ohnishi, M. Homma, K. Kutsukake, and T. Iino, J. Bacteriol, 169:1485-1488, 1987). This phenomenon allowed hook-basal body complexes from such mutants to be purified and analyzed by electron microscopy and gel electrophoresis. The absence of the P and L rings in such structures was found to correlate with the absence of proteins of apparent molecular weight 39,000 and 26,000, respectively. Gene-polypeptide correlations from other studies enabled us to complete gene-polypeptide-structure correspondences for these two proteins as flaM----39-kilodalton protein----P ring and flaY----26-kilodalton protein----L ring.