Extended x-ray absorption fine structure studies on the iron-containing subunit of ribunucleotide reductase from Escherichia coli

Journal Article · Tue Jul 28 04:00:00 EDT 1987 · Biochemistry; (United States)

OSTI ID:5970103

Bunker, G; Petersson, L; Sjoeberg, B M; Sahlin, M; Chance, M; Chance, B; Ehrenberg, A

Iron K-edge X-ray absorption spectra were obtained on the protein B2, the small subunit of ribonucleotide reductase from Escherichia coli. Protein B2 contains a binuclear iron center with many properties in common with the iron center of oxidized hemerythrins. The extended x-ray absorption fine structure (EXAFS) measurements on protein B2 were analyzed and compared with published data for oxyhemerythrin. In protein B2 there are, in the first coordination shell around each Fe atom, five or six oxygen or nitrogen atoms that are directly coordinated ligands. In oxyhemerythrin there are six ligands to each iron. As in oxyhemerythrin, one of the ligands in the first shell of protein B2 is at a short distance, about 1.78 A, confirming the existence of a ..mu..-oxo bridge. The other atoms of the first shell are at an average distance of 2.04 A, which is about 0.1 A shorter than in oxyhemerythrin. In protein B2 the Fe-Fe distance is in the range 3.26-3.48 A, and the bridging angle falls between 130 and 150/sup 0/. On the basis of these data, there is no direct evidence for any histidine ligands in protein B2, but the noise level leaves way for the possibility of a maximum of about three histidines for each Fe pair. The x-ray absorption spectrum of a hydroxyurea-treated sample was not significantly different from that of the native protein B2, which implies that no significant alteration in the structure of the iron site occurs upon destruction of the tyrosine radical.

• Research Organization: Institute for Structural and Functional Studies, Philadelphia, PA
• OSTI ID: 5970103
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:15; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

560120* -- Radiation Effects on Biochemicals
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63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AMINO ACIDS
AZOLES
BACTERIA
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
CARBOXYLIC ACIDS
ENZYMES
ESCHERICHIA COLI
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HISTIDINE
IMIDAZOLES
IRON COMPOUNDS
LIGANDS
MICROORGANISMS
NUCLEOTIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDOREDUCTASES
RADIATION EFFECTS
SPECTRA
TRANSITION ELEMENT COMPOUNDS
X-RAY SPECTRA