Localization of proteins controlling motility and chemotaxis in Escherichia coli

Abstract

Flagellar proteins controlling motility and chemotaxis in Escherichia coli were selectively labeled in vivo with [35S]methionine. This distribution of these proteins in subcellular fractions was examined by sodium dodecyl sulfatepolyacrylamide gel electrophoresis and autoradiography. The motA, motB, cheM, and cheD gene products were found to be confined exclusively to the inner cytoplasmic membrane fraction, whereas the cheY, cheW, and cheA (66,000 daltons) polypeptides appeared only in the soluble cytoplasmic fraction. The cheB, cheX, cheZ, and cheA (76,000 daltons) proteins, however, were distributed in both the cytoplasm and the inner membrane fractions. The hag gene product (flagellin) was the only flagellar protein examined that copurified with the outer lipopolysaccharide membrane. Differences in the intracellular locations of the che and mot gene prodcuts presumably reflect the functional attributes of these components.