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Publication Abstract from PubMed

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.

H662 is the linchpin of ATP hydrolysis in the nucleotide-binding domain of the ABC transporter HlyB.,Zaitseva J, Jenewein S, Jumpertz T, Holland IB, Schmitt L EMBO J. 2005 Jun 1;24(11):1901-10. Epub 2005 May 12. PMID:15889153^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.