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Crystallographic Study of Azide-inhibited Bovine Cu,Zn Superoxide Dismutase

1994; Elsevier BV; Volume: 240; Issue: 3 Linguagem: Inglês

10.1006/jmbi.1994.1432

1089-8638

Kristina Djinović‐Carugo, Fabio Polticelli, Alessandro Desideri, Giuseppe Rotilio, Keith S. Wilson, Martino Bolognesi,

Metal complexes synthesis and properties

The crystal structure of azide-inhibited bovine Cu,Zn superoxide dismutase has been studied and refined based on X-ray synchrotron radiation data, in conjunction with difference Fourier and restrained crystallographic refinement techniques. The final R-factor for the 20,756 reflections in the 10·0 to 2·1 Å resolution range is 0·166. In both enzyme subunits, the azide anion, which is a competitive inhibitor expected to mimic the superoxide binding mode, is observe directly coordinated to the Cu2+ at the place of the metal-bound water molecule, forming an ion pair with the conserved active site residue Arg141. The coordination sphere of Cu2+ is partly altered with respect to the uninhibited enzyme: a displacement of 0·67 Å in subunit A, and 0·37 Å in subunit B of the dimeric enzyme is observed for the Cu2+. Only two ligands in the Cu2+ coordination sphere (His46 and His118) are affected by azide binding, whereas virtually no rearrangement of the Zn2+ ligands is reported.