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Publication Abstract from PubMed

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 Mg2+ ion is present in each of the two active sites in this homodimeric enzyme, and two water molecules are coordinated with each Mg2+ 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 the context of DNA binding and cleavage.

Structure, flexibility, and mechanism of the Bacillus stearothermophilus RecU Holliday junction resolvase.,Kelly SJ, Li J, Setlow P, Jedrzejas MJ Proteins. 2007 Sep 1;68(4):961-71. PMID:17557334^[1]

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