ISSN:
1399-0047
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
The three-dimensional crystal structure of Serratia marcescens endonuclease has been refined at 1.1 Å resolution to an R factor of 12.9% and an Rfree of 15.6% with the use of anisotropic temperature factors. The model contains 3694 non-H atoms, 715 water molecules, four sulfate ions and two Mg2+-binding sites at the active sites of the homodimeric protein. It is shown that the magnesium ion linked to the active-site Asn119 of each monomer is surrounded by five water molecules and shows an octahedral coordination geometry. The temperature factors for the bound Mg2+ ions in the A and B subunits are 7.08 and 4.60 Å2, respectively, and the average temperature factors for the surrounding water molecules are 12.13 and 10.3 Å2, respectively. In comparison with earlier structures, alternative side-chain conformations are defined for 51 residues of the dimer, including the essential active-site residue Arg57. A plausible mechanism of enzyme function is proposed based on the high-resolution S. marcescens nuclease structure, the functional characteristics of the natural and mutational forms of the enzyme and consideration of its structural analogy with homing endonuclease I-PpoI.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S090744490000322X
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