Rubredoxin from the green sulfur bacterium Chlorobium tepidum functions as an electron acceptor for pyruvate ferredoxin oxidoreductase

Ki Seok Yoon, Russ Hille, Craig Hemann, F. Robert Tabita

Research output: Contribution to journalArticle

51 Citations (Scopus)

Abstract

Rubredoxin (Rd) from the moderately thermophilic green sulfur bacterium Chlorobium tepidum was found to function as an electron acceptor for pyruvate ferredoxin oxidoreductase (PFOR). This enzyme, which catalyzes the conversion of pyruvate to acetyl-CoA and CO2, exhibited an absolute dependence upon the presence of Rd. However, Rd was incapable of participating in the pyruvate synthase or CO2 fixation reaction of C. tepidum PFOR, for which two different reduced ferredoxins are employed as electron donors. These results suggest a specific functional role for Rd in pyruvate oxidation and provide the initial indication that the two important physiological reactions catalyzed by PFOPJ pyruvate synthase are dependent on different electron carriers in the cell. The UV-visible spectrum of oxidized Rd, with a monomer molecular weight of 6500, gave a molar absorption coefficient at 492 nm of 6.89 mM-1 cm-1 with an A492/A280 ratio of 0.343 and contained one iron atom/molecule. Further spectroscopic studies indicated that the CD spectrum of oxidized C. tepidum Rd exhibited a unique absorption maximum at 385 nm and a shoulder at 420 nm. The EPR spectrum of oxidized Rd also exhibited unusual anisotropic resonances at g = 9.675 and g = 4.322, which is composed of a narrow central feature with broader shoulders to high and low field. The midpoint reduction potential of C. tepidum Rd was determined to be -87 mV, which is the most electronegative value reported for Rd from any source.

Original languageEnglish
Pages (from-to)29772-29778
Number of pages7
JournalJournal of Biological Chemistry
Volume274
Issue number42
DOIs
Publication statusPublished - Oct 15 1999
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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