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Structure, flexibility, and mechanism of the Bacillus stearothermophilus RecU holliday junction resolvase
Author(s) -
Kelly Stephen J.,
Li Jie,
Setlow Peter,
Jedrzejas Mark J.
Publication year - 2007
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.21418
Subject(s) - holliday junction , tn3 transposon , chemistry , dna , stereochemistry , molecule , base pair , crystallography , biophysics , biology , biochemistry , dna repair , mutant , transposable element , organic chemistry , gene
Here we report a high resolution structure of RecU‐Holliday junction resolvase from Bacillus stearothermophilus. The functional unit of RecU is a homodimer that contains a “mushroom” like structure with a rigid cap and two highly flexible loops extending outwards. These loops appear to be highly flexible/dynamic, and presumably are directly involved in DNA binding and holding it for catalysis. Structural modifications of both the protein and DNA upon their interaction are essential for catalysis. An Mg 2+ ion is present in each of the two active sites in this homodimeric enzyme, and two water molecules are coordinated with each Mg 2+ ion. Our data are consistent with one of these water molecules acting as a nucleophile and the other as a general acid. The identities of the general base and general acid involved in catalysis and the Lewis acid that stabilizes the pentacovalent transition state phosphate ion are proposed. A model for the RecU‐Holliday junction DNA complex is also proposed and discussed in thecontext of DNA binding and cleavage. Proteins 2007. © 2007 Wiley‐Liss, Inc.