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  • The EMBO Journal (2006) 25, 1426 - 1435
  • doi:10.1038/sj.emboj.7601036

Published online: 9 March 2006

XpsE oligomerization triggered by ATP binding, not hydrolysis, leads to its association with XpsL

Sheng-Jie Shiue1, Ko-Min Kao1, Wei-Ming Leu2, Ling-Yun Chen3, Nei-Li Chan1 and Nien-Tai Hu1

  1. Institute of Biochemistry, National Chung Hsing University, Taichung, Taiwan, Republic of China
  2. Institute of Biotechnology, National Chung Hsing University, Taichung, Taiwan, Republic of China
  3. Institute of Biochemistry, Chung Shan Medical University, Taichung, Taiwan, Republic of China

Correspondence to:

Nien-Tai Hu, Institute of Biochemistry, National Chung Hsing University, 250 Kuo Kuang Road, Taichung 402, Taiwan, Republic of China. Tel.: +886 4 2285 3486 ext. 228; Fax: +886 4 2285 3487; E-mail: nthu@nchu.edu.tw

Received 20 September 2005; Accepted 14 February 2006

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.

  • Keywords:

    • ATP binding,
    • GspE–GspL interaction,
    • GspE oligomerization,
    • type II secretion system,
    • Xanthomonas campestris
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