Article
- The EMBO Journal (2005) 24, 1901 - 1910
- doi:10.1038/sj.emboj.7600657
Published online: 12 May 2005
Subject Categories:
H662 is the linchpin of ATP hydrolysis in the nucleotide-binding domain of the ABC transporter HlyB
Jelena Zaitseva1,a, Stefan Jenewein1,a, Thorsten Jumpertz1, I Barry Holland2 and Lutz Schmitt1
- Institute of Biochemistry, Biocenter, Johann-Wolfgang Goethe University Frankfurt, Frankfurt, Germany
- Institut de Génétique et Microbiologie, Bât. 409, Université de Paris XI, Orsay, France
Correspondence to:
Lutz Schmitt, Institute of Biochemistry, Biocenter, Johann-Wolfgang Goethe University Frankfurt, Marie Curie Strasse 9, 60439 Frankfurt, Germany. Tel.: +49 69 79829 569; Fax: +49 69 79829 495; E-mail: lschmitt@em.uni-frankfurt.de
aThese authors contributed equally to this work
Received 30 September 2004; Accepted 23 March 2005
Abstract
The ABC transporter HlyB is a central element of the HlyA secretion machinery, a paradigm of Type I secretion. Here, we describe the crystal structure of the HlyB-NBD (nucleotide-binding domain) with H662 replaced by Ala in complex with ATP/Mg2+. The dimer shows a composite architecture, in which two intact ATP molecules are bound at the interface of the Walker A motif and the C-loop, provided by the two monomers. ATPase measurements confirm that H662 is essential for activity. Based on these data, we propose a model in which E631 and H662, highly conserved among ABC transporters, form a catalytic dyad. Here, H662 acts as a 'linchpin', holding together all required parts of a complicated network of interactions between ATP, water molecules, Mg2+, and amino acids both in cis and trans, necessary for intermonomer communication. Based on biochemical experiments, we discuss the hypothesis that substrate-assisted catalysis, rather than general base catalysis might operate in ABC-ATPases.
Keywords:
- ATPase activity,
- catalysis,
- membrane transporter,
- NBD-dimer,
- X-ray crystallography
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