Resonance Raman studies of Escherichia coli sulfite reductase hemoprotein. 2. Fe sub 4 S sub 4 cluster vibrational modes
- Duke Univ. Medical Center, Durham, NC (USA)
- Princeton Univ., NJ (USA)
Resonance Raman (RR) spectra from the hemoprotein subunit of Escherichia coli sulfite reductase (SiR-HP) are examined in the low-frequency (200-500 cm{sup {minus}1}) region where Fe-S stretching modes are expected. In spectra obtained with excitation in the siroheme Soret or Q bands, this region is dominated by siroheme modes. Modes assignable to the Fe{sub 4}S{sub 4} cluster are selectively enhanced, however, with excitation at 488.0 or 457.9 nm. The assignments are confirmed by observation of the expected frequency shifts in SiR-HP extracted from E. coli grown on {sup 34}S-labeled sulfate. The mode frequencies and isotopic shifts resemble those seen in RR spectra of other Fe{sub 4}S{sub 4} proteins and analogues, but the breathing mode of the cluster at 342 cm{sup {minus}1} is higher than that observed in the other species. Spectra of various ligand complexes of SiR-HP reveal only slight sensitivity of the cluster terminal ligand modes to the presence of exogenous heme ligands, at variance with a model of ligand binding in a bridged mode between heme and cluster. Close examination of RR spectra obtained with siroheme Soret-band excitation reveals additional {sup 34}S-sensitive features at 352 and 393 cm{sup {minus}1}. These may be attributed to a bridging thiolate ligand.
- OSTI ID:
- 5028758
- Journal Information:
- Biochemistry; (USA), Vol. 28:13; ISSN 0006-2960
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
METALLOPROTEINS
RAMAN SPECTROSCOPY
ESCHERICHIA COLI
IRON COMPOUNDS
LIGANDS
MOLECULAR STRUCTURE
SPECTRAL SHIFT
SULFITES
SULFUR 34
BACTERIA
EVEN-EVEN NUCLEI
ISOTOPES
LASER SPECTROSCOPY
LIGHT NUCLEI
MICROORGANISMS
NUCLEI
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PROTEINS
SPECTROSCOPY
STABLE ISOTOPES
SULFUR COMPOUNDS
SULFUR ISOTOPES
TRANSITION ELEMENT COMPOUNDS
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