Integral membrane proteins required for bacterial motility and chemotaxis.

Several of the gene products required for bacterial motility and chemotaxis are integral components of the cytoplasmic membrane. Amplification of the expression of one of these genes, motB, using in vitro recombinant DNA techniques, has allowed us to initiate a study of the assembly of this protein into the membrane. The identical sizes of the motB gene products synthesised in vivo and in vitro strongly suggest that assembly is achieved without the involvement of a proteolytically processed leader peptide. Further analysis of this system should yield valuable insights into the specific determinants of the cellular localisation of the motB gene product. Two other membrane proteins, the tsr and tar products have been studied in relation to their role as integrating channels for the transfer of sensory information into the bacterial cell. A model of the functional properties of these proteins is presented and discussed in terms of recent findings that they are subject to multiple covalent modifications during sensory adaptation.