Resonance Raman studies of Escherichia coli sulfite reductase hemoprotein. 1. Siroheme vibrational modes.

Published

Journal Article

Resonance Raman (RR) spectra are reported for the hemoprotein subunit (SiR-HP) of Escherichia coli NADPH-sulfite reductase (EC 1.8.1.2) in various ligation and redox states. Comparison of the RR spectra of extracted siroheme and the mu-oxo FeIII dimer of octaethylisobacteriochlorin with those of mu-oxo FeIII octaethylchlorin dimer and mu-oxo FeIII octaethylporphyrin dimer demonstrates that many siroheme bands can be correlated with established porphyrin skeletal modes. Depolarization measurements are a powerful tool in this correlation, since the 45 degrees rotation of the C2 symmetry axis of the isobacteriochlorin ring relative to the chlorin system results in reversal of the polarization properties (polarized vs anomalously polarized) of bands correlating with B1g and B2g modes of porphyrin. Various SiR-HP adducts (CO, NO, CN-, SO3(2-] show upshifted high-frequency bands, characteristic of the low-spin state and consistent with the expected core size sensitivity of the skeletal modes. Fully reduced unliganded SiR-HP (both siroheme and Fe4S4 cluster reduced) in liquid solution displays RR features comparable to those of high-spin ferrous porphyrins; on freezing, the RR spectrum changes, reflecting an apparent mixture of siroheme spin states. At intermediate reduction levels in solution a RR species is observed whose high-frequency bands are upshifted relative to oxidized and fully reduced SiR-HP. This spectrum, thought to arise from the "one-electron" state of SiR-HP (siroheme reduced, cluster oxidized), may be due to S = 1 FeII siroheme.

Full Text

Duke Authors

Cited Authors

  • Han, SH; Madden, JF; Thompson, RG; Strauss, SH; Siegel, LM; Spiro, TG

Published Date

  • June 27, 1989

Published In

Volume / Issue

  • 28 / 13

Start / End Page

  • 5461 - 5471

PubMed ID

  • 2673346

Pubmed Central ID

  • 2673346

International Standard Serial Number (ISSN)

  • 0006-2960

Digital Object Identifier (DOI)

  • 10.1021/bi00439a022

Language

  • eng

Conference Location

  • United States