UNSPECIFIED (2000) X-ray crystallographic study of cyanide binding provides insights into the structure-function relationship for cytochrome cd(1) nitrite reductase from Paracoccus pantotrophus. JOURNAL OF BIOLOGICAL CHEMISTRY, 275 (33). pp. 25089-25094. ISSN 0021-9258

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Abstract

We present a 1.59-Angstrom resolution crystal structure of reduced Paracoccus pantotrophus cytochrome ed, with cyanide bound to the d(1) heme and His/Met coordination of the c heme. Fe-C-N bond angles are 146 degrees for the A subunit and 164 degrees for the B subunit of the dimer, The nitrogen atom of bound cyanide is within hydrogen bonding distance of His(345) and His(388) and either a water molecule in subunit A or Tyr(25), subunit B. The ferrous heme-cyanide complex is unusually stable (K-d similar to 10-(6) M); we propose that this reflects both the design of the specialized d(1) heme ring and a general feature of anion reductases with active site heme, Oxidation of crystals of reduced, cyanide-bound, cytochrome cd(1) results in loss of cyanide and return to the native structure with Tyr(25) as a ligand to the d(1) heme iron and switching to His/His coordination at the c-type heme, No reason for unusually weak binding of cyanide to the ferric state can be identified; rather it is argued that the protein is designed such that a chelate-based effect drives displacement by tyrosine of cyanide or a weaker ligand, like reaction product nitric oxide, from the ferric d(1) heme.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry
Journal or Publication Title:	JOURNAL OF BIOLOGICAL CHEMISTRY
Publisher:	AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
ISSN:	0021-9258
Date:	18 August 2000
Volume:	275
Number:	33
Number of Pages:	6
Page Range:	pp. 25089-25094
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/13075

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