1xmv
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"E. Coli RecA in complex with MgADP"
OverviewOverview
RecA catalyzes the DNA pairing and strand-exchange steps of homologous, recombination, an important mechanism for repair of double-stranded DNA, breaks. The binding of RecA to DNA is modulated by adenosine nucleotides., ATP increases the affinity of RecA for DNA, while ADP decreases the, affinity. Previously, the crystal structures of E. coli RecA and its, complex with ADP have been determined to resolutions of 2.3 and 3.0 A, respectively, but the model for the RecA-ADP complex did not include, magnesium ion or side chains. Here, we have determined the crystal, structures of RecA in complex with MgADP and MnAMP-PNP, a nonhydrolyzable, analogue of ATP, at resolutions of 1.9 and 2.1 A, respectively. Both, crystals grow in the same conditions and have RecA in a right-handed, helical form with a pitch of approximately 82 A. The crystal structures, show the detailed interactions of RecA with the nucleotide cofactors, including the metal ion and the gamma phosphate of AMP-PNP. There are very, few conformational differences between the structures of RecA bound to ADP, and AMP-PNP, which differ from uncomplexed RecA only in a slight opening, of the P-loop residues 66-73 upon nucleotide binding. To interpret the, functional significance of the structure of the MnAMP-PNP complex, a, coprotease assay was used to compare the ability of different nucleotides, to promote the active, extended conformation of RecA. Whereas ATPgammaS, and ADP-AlF(4) facilitate a robust coprotease activity, ADP and AMP-PNP do, not activate RecA at all. We conclude that the crystal structure of the, RecA-MnAMP-PNP complex represents a preisomerization state of the RecA, protein that exists after ATP has bound but before the conformational, transition to the active state.
About this StructureAbout this Structure
1XMV is a Single protein structure of sequence from Escherichia coli with MG and ADP as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structures of Escherichia coli RecA in complex with MgADP and MnAMP-PNP., Xing X, Bell CE, Biochemistry. 2004 Dec 28;43(51):16142-52. PMID:15610008
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