title: A novel DnaJ-like protein in Escherichia coli inserts into the cytoplasmic membrane with a type III topology.
abstract: We describe a novel Escherichia coli protein, DjlA, containing a highly conserved J-region motif, which is present in the DnaJ protein chaperone family and required for interaction with DnaK. Remarkably, DjlA is shown to be a membrane protein, localized to the inner membrane with the unusual Type III topology (N-out, C-in). Thus, DjlA appears to present an extremely short N-terminus to the periplasm and has a single transmembrane domain (TMD) and a large cytoplasmic domain containing the C-terminal J-region. Analysis of the TMD of DjlA and recently identified homologues in Coxiella burnetti and Haemophilus influenzae revealed a striking pattern of conserved glycines (or rarely alanine), with a four-residue spacing. This motif, predicted to form a spiral groove in the TMD, is more marked than a repeating glycine motif, implicated in the dimerization of TMDs of some eukaryotic proteins. This feature of DjlA could represent a promiscuous docking mechanism for interaction with a variety of membrane proteins. DjlA null mutants can be isolated but these appear rapidly to accumulate suppressors to correct envelope and growth defects. Moderate (10-fold) overproduction of DjlA suppresses a mutation in FtsZ but markedly perturbs cell division and cell-envelope growth in minimal medium. We propose that DjlA plays a role in the correct assembly, activity and/or maintenance of a number of membrane proteins, including two-component signal-transduction systems.
authors.affiliation: Institut de Génétique et Microbiologie, URA 1354, Université Paris-Sud, Orsay, France.
authors.forename: D J
authors.initials: DJ
authors.lastname: Clarke
authors.forename: A
authors.initials: A
authors.lastname: Jacq
authors.forename: I B
authors.initials: IB
authors.lastname: Holland
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002457:Cell Extracts; D002462:Cell Membrane / Q000378:metabolism; D003470:Culture Media; D003598:Cytoskeletal Proteins; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D011134:Polysaccharides; D011135:Polysaccharides, Bacterial; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D002457:Cell Extracts; D003470:Culture Media; D003598:Cytoskeletal Proteins; C494634:DjlA protein, E coli; C494635:DnaJ protein, E coli; D029968:Escherichia coli Proteins; C071525:FtsZ protein, Bacteria; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D011134:Polysaccharides; D011135:Polysaccharides, Bacterial; D011993:Recombinant Fusion Proteins; C004275:colanic acid