Sequences of Homologs to the Bacterial Coat Protein CexE and Model for Secetion of CexE to the Outer Membrane

Fasta formatted protein sequences of CexE variants from several pathogenic species of bacteria. These proteins have been shown to be outer membrane coat proteins in enterotoxigenic (ETEC) and enteroaggregative (EAEC) Escherichia coli, and C. rodentium. Additionally, CexE has been shown to enhance the pathogenicity of C. rodentium in murine infection studies. The CexE polypeptide is transported from the cytoplasm to the periplasm by the SecYEG complex. Secretion across the outer membrane requires five additional genes named cexPABCD or aatPABCD depending on the species. CexC is predicted to be a cytosolic ATPase. Mutations in cexC abolish secretion of CexC to the outer membrane and attenuate C. rodentium virulence in murine infection models. CexP and CexD are predicted to be inner membrane proteins with several transmembrane helices each. CexA is likely an outer membrane beta-barrel protein as it has homology to TolC. The majority of CexB likely resides in the periplamsic where it may function in a manner analogous to membrane fusion proteins of Type I secretion systems.