title: XpsE oligomerization triggered by ATP binding, not hydrolysis, leads to its association with XpsL.
abstract: GspE belongs to a secretion NTPase superfamily, members of which are involved in type II/IV secretion, type IV pilus biogenesis and DNA transport in conjugation or natural transformation. Predicted to be a cytoplasmic protein, GspE has nonetheless been shown to be membrane-associated by interacting with the N-terminal cytoplasmic domain of GspL. By taking biochemical and genetic approaches, we observed that ATP binding triggers oligomerization of Xanthomonas campestris XpsE (a GspE homolog) as well as its association with the N-terminal domain of XpsL (a GspL homolog). While isolated XpsE exhibits very low intrinsic ATPase activity, association with XpsL appears to stimulate ATP hydrolysis. Mutation at a conserved lysine residue in the XpsE Walker A motif causes reduction in its ATPase activity without significantly influencing its interaction with XpsL, congruent with the notion that XpsE-XpsL association precedes ATP hydrolysis. For the first time, functional significance of ATP binding to GspE in type II secretion system is clearly demonstrated. The implications may also be applicable to type IV pilus biogenesis.
authors.affiliation: Institute of Biochemistry, National Chung Hsing University, Taichung, Taiwan, Republic of China.
authors.forename: Sheng-Jie
authors.initials: SJ
authors.lastname: Shiue
authors.forename: Ko-Min
authors.initials: KM
authors.lastname: Kao
authors.forename: Wei-Ming
authors.initials: WM
authors.lastname: Leu
authors.forename: Ling-Yun
authors.initials: LY
authors.lastname: Chen
authors.forename: Nei-Li
authors.initials: NL
authors.lastname: Chan
authors.forename: Nien-Tai
authors.initials: NT
authors.lastname: Hu
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry; D000255:Adenosine Triphosphate / Q000737:chemistry*; D000266:Adenylyl Imidodiphosphate / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001704:Biopolymers / Q000737:chemistry; D006868:Hydrolysis; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016959:Xanthomonas campestris / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D001704:Biopolymers; D026901:Membrane Transport Proteins; C071567:general secretion pathway protein, Xanthomonas campestris; D000266:Adenylyl Imidodiphosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate