title: The transmembrane domain of the DnaJ-like protein DjlA is a dimerisation domain.
abstract: DjlA is a bitopic inner membrane protein, which belongs to the DnaJ co-chaperone family in Escherichia coli. Overproduction of DjlA leads to the synthesis of colanic acid, resulting in mucoidy, via the activation of the two-component regulatory system RcsC/B that controls the cps (capsular polysaccharide) operon. This induction requires both the co-chaperone activity of DjlA, in cooperation with DnaK and GrpE, and its unique transmembrane (TM) domain. Here, we show that the TM segment of DjlA acts as a dimerisation domain: when fused to the N-terminal DNA-binding domain of the lambda cI repressor protein, it can substitute for the native C-terminal dimerisation domain of cI, thus generating an active cI repressor. Replacing the TM domain of DjlA by other TM domains, with or without dimerising capacity, revealed that dimerisation is not sufficient for the induction of cps expression, indicating an additional sequence- or structurally specific role for the TM domain. Finally, the conserved glycines present in the TM domain of DjlA are essential for the induction of mucoidy, but not for dimerisation.
authors.affiliation: Institut de Génétique et Microbiologie, UMR CNRS 8621, Bâtiment 400, Université Paris-Sud, 91405 Orsay, France.
authors.forename: C M
authors.initials: CM
authors.lastname: Toutain
authors.forename: D J
authors.initials: DJ
authors.lastname: Clarke
authors.forename: J A
authors.initials: JA
authors.lastname: Leeds
authors.forename: J
authors.initials: J
authors.lastname: Kuhn
authors.forename: J
authors.initials: J
authors.lastname: Beckwith
authors.forename: I B
authors.initials: IB
authors.lastname: Holland
authors.forename: A
authors.initials: A
authors.lastname: Jacq
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D004268:DNA-Binding Proteins; D019281:Dimerization; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007763:Lac Operon; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C494634:DjlA protein, E coli; C494635:DnaJ protein, E coli; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins