THE CRYSTAL STRUCTURE OF ECORV ENDONUCLEASE AND OF ITS COMPLEXES WITH COGNATE AND NON-COGNATE DNA SEGMENTS

摘要: The crystal structure of EcoRV endonuclease has been determined at 2.5 A resolution and that its complexes with the cognate DNA decamer GGGATATCCC (recognition sequence underlined) non-cognate octamer CGAGCTCG 3.0 resolution. Two duplexes DNA, stacked end-to-end, are bound to dimeric enzyme in B-DNA-like conformations. protein--DNA interactions this complex prototypic for non-specific binding. In contrast, only one duplex is deviates considerably from canonical B-form DNA. Most notably, a kink approximately 50 degrees observed central TA step concomitant compression major groove. Base-specific hydrogen bonds between recognition base pairs occur exclusively These appear highly co-operative as they all made through short surface loop comprising residues 182-186. Numerous contacts sugar phosphate backbone extending beyond both types complex. However, total area buried on formation > 1800 A2 larger case acidic side chains, Asp74 Asp90, close reactive phosphodiester group most probably provide oxygen ligands binding essential cofactor Mg2+. An important role also indicated Lys92, which together two functions appears be conserved otherwise unrelated EcoRI endonuclease. structural results give new insight into physical basis remarkable specificity enzyme.