Resonance Raman studies of Escherichia coli sulfite reductase hemoprotein. 2. Fe sub 4 S sub 4 cluster vibrational modes

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...

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Bibliographic Details
Published in:Biochemistry (Easton) 1989-06, Vol.28:13
Main Authors: Madden, J.F., Siegel, L.M., Han, Sanghwa, Spiro, T.G.
Format: Article
Language:English
Subjects:
550601 - Medicine- Unsealed Radionuclides in Diagnostics
BACTERIA
ESCHERICHIA COLI
EVEN-EVEN NUCLEI
IRON COMPOUNDS
ISOTOPES
LASER SPECTROSCOPY
LIGANDS
LIGHT NUCLEI
METALLOPROTEINS
MICROORGANISMS
MOLECULAR STRUCTURE
NUCLEI
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PROTEINS
RADIOLOGY AND NUCLEAR MEDICINE
RAMAN SPECTROSCOPY
SPECTRAL SHIFT
SPECTROSCOPY
STABLE ISOTOPES
SULFITES
SULFUR 34
SULFUR COMPOUNDS
SULFUR ISOTOPES
TRANSITION ELEMENT COMPOUNDS
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Summary: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.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi00439a023