View source for 1xef

[[Image:1xef.gif|left|200px]]

 {{Structure
|PDB= 1xef |SIZE=350|CAPTION= <scene name='initialview01'>1xef</scene>, resolution 2.50&Aring;
|SITE= 
|LIGAND= <scene name='pdbligand=MG:MAGNESIUM+ION'>MG</scene> and <scene name='pdbligand=ATP:ADENOSINE-5'-TRIPHOSPHATE'>ATP</scene>
|ACTIVITY= 
|GENE= 
}}

'''Crystal structure of the ATP/Mg2+ bound composite dimer of HlyB-NBD'''


==Overview==
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.

==About this Structure==
1XEF is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1XEF OCA]. 

==Reference==
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:[http://www.ncbi.nlm.nih.gov/pubmed/15889153 15889153]
[[Category: Escherichia coli]]
[[Category: Single protein]]
[[Category: Holland, I B.]]
[[Category: Jenewein, S.]]
[[Category: Schmitt, L.]]
[[Category: Zaitseva, J.]]
[[Category: ATP]]
[[Category: MG]]
[[Category: abc-transporter]]
[[Category: atp-dependent transport protein]]
[[Category: atpase]]
[[Category: haemolysin b]]

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