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Titolo:
EXAFS STUDIES OF UTEROFERRIN AND ITS ANION COMPLEXES
Autore:
TRUE AE; SCARROW RC; RANDALL CR; HOLZ RC; QUE L;
Indirizzi:
UNIV MINNESOTA,DEPT CHEM MINNEAPOLIS MN 55455 UNIV MINNESOTA,DEPT CHEM MINNEAPOLIS MN 55455 HAVERFORD COLL HAVERFORD PA 19041
Titolo Testata:
Journal of the American Chemical Society
fascicolo: 10, volume: 115, anno: 1993,
pagine: 4246 - 4255
SICI:
0002-7863(1993)115:10<4246:ESOUAI>2.0.ZU;2-R
Fonte:
ISI
Lingua:
ENG
Soggetto:
PURPLE ACID-PHOSPHATASE; X-RAY-ABSORPTION; PIG ALLANTOIC FLUID; IRON OXO PROTEINS; TRANSITION-METAL COMPLEXES; FINE-STRUCTURE SPECTROSCOPY; ELECTRON-PARAMAGNETIC-RES; MAGNETIC-PROPERTIES; MOLECULAR-STRUCTURE; BEEF SPLEEN;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
112
Recensione:
Indirizzi per estratti:
Citazione:
A.E. True et al., "EXAFS STUDIES OF UTEROFERRIN AND ITS ANION COMPLEXES", Journal of the American Chemical Society, 115(10), 1993, pp. 4246-4255

Abstract

Iron K-edge X-ray absorption data on the purple acid phosphatase fromporcine uterus (uteroferrin, Uf) have been obtained for the native reduced enzyme and for the oxidized enzyme in its phosphate- and arsenate-bound forms. In all three complexes, the first sphere consists of 1.5 N/O at approximately 1.94 angstrom, 4 N/O at approximately 2.1 angstrom, and 0.5-1 N/O at approximately 2.4 angstrom; in no complex is found an Fe-O bond of approximately 1.8 angstrom which would derive from a mu-oxo bond. The approximately 1.94-angstrom shell corresponds to Fe-OAr and Fe-mu-OH(or R) bonds. The approximately 2.1-angstrom shell arises from histidine, carboxylate, oxoanion, and solvent ligation. The scatterer at approximately 2.4 angstrom is associated with a chelated carboxylate residue. The second-sphere analysis for Uf(r) indicates anFe-Fe distance of 3.52 angstrom, similar to those found for semimethemerythrin azide, methane monooxygenase, and related model complexes, which suggests the presence of a (mu-hydroxo or alkoxo)diiron unit supported by a carboxylate bridge. On the basis of the EXAFS analysis and other spectroscopic data, it is proposed that tyrosine and histidine are terminal ligands to the Fe(III) center, and histidine and the chelated carboxylate coordinate to the Fe(II) center, with solvent molecules completing the diiron coordination sphere. This proposed active siteis slightly modified from that found for the R2 protein of ribonucleotide reductase from Escherichia coli and suggested for the hydroxylasecomponent of methane monooxygenase. The diiron cores of Uf(o).PO4 andUf(o).AsO4 are significantly different from that of Uf(r). Given the absence of a 1.8-angstrom bond, the diferric sites are not oxo-bridged, a conclusion also corroborated by the small intensity of the 1s --> 3d preedge features in these complexes. The Fe-Fe distances of approximately 3.2-3.3 angstrom found for Uf(o).PO4 and Uf(o).AsO4 must then arise from an Fe2(OR)2 core. The observed Fe-P (3.17 angstrom) and Fe-As (3.41 angstrom) distances correspond to Fe-O-P(As) angles indicativeof a bidentate bridging oxoanion which supports the Fe2O2 core.

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Documento generato il 01/12/20 alle ore 13:37:09