Identification of a hydroxide ligand at the iron center of ribonucleotide reductase by resonance Raman spectroscopy

Journal Article · Tue Jul 14 04:00:00 EDT 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00388a010· OSTI ID:6030530

Sjoeberg, B; Sanders-Loehr, J; Loehr, T M

The resonance Raman spectrum of protein B2 of ribonucleotide reductase from Escherichia coli shows several features related to its oxo-bridged binuclear iron center. A peak at 492 cm/sup -1/ is assigned to the symmetric stretch of the Fe-O-Fe moiety on the basis of its 13-cm/sup -1/ shift to lower energy upon /sup 18/O substitution. The /sup 18/O species shows an additional peak at 731 cm/sup -1/, which is a good candidate for the asymmetric stretch of the Fe-O-Fe moiety. Its exact location in the /sup 16/O species is obscured by the presence of a protein tryptophan vibration at 758 cm/sup -1/. A third resonance-enhanced peak at 598 cm/sup -1/ is identified as an Fe-OH vibration on the basis of its 24-cm/sup -1/ shift to lower energy in H/sub 2//sup 18/O, its 2-cm/sup -1/ shift to lower energy in D/sub 2/O, and its pH-dependent intensity. A hydrogen-bonded ..mu..-oxo bridge similar to that in hemerythrin is suggested by the unusually low frequency for the Fe-O-Fe symmetric stretch and the 3-cm/sup -1/ shift to higher energy of nu/sub s/ (Fe-O-Fe), an Fe-O-Fe angle of 138/sup 0/ can be calculated. This small angle suggests that the iron center consists of a tribridged core as in hemerythrin. A model for the binuclear iron center of ribonucleotide reductase is presented in which the hydroxide ligand sites provide an explanation for the half-of-sites reactivity of the enzyme.

• Research Organization: Swedish Univ. of Agricultural Sciences, Uppsala
• OSTI ID: 6030530
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:14; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
BACTERIA
ELEMENTS
ENZYMES
ESCHERICHIA COLI
EVEN-EVEN NUCLEI
HEAVY WATER
HYDROGEN COMPOUNDS
IRON
ISOTOPES
LASER SPECTROSCOPY
LIGANDS
LIGHT NUCLEI
METALS
MICROORGANISMS
MOLECULAR STRUCTURE
NUCLEI
OXIDOREDUCTASES
OXYGEN 18
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
RAMAN SPECTRA
RAMAN SPECTROSCOPY
SPECTRA
SPECTROSCOPY
STABLE ISOTOPES
TRANSITION ELEMENTS
WATER