Journal article

Publication year: 2003

Pages: 197-204

Journal: Archives of Microbiology

Volume number: 179

Issue number: 3

ISSN: 0302-8933

eISSN: 1432-072X

DOI Link: https://doi.org/10.1007/s00203-003-0517-8

Publisher: Springer

Abstract: 
The key step in the fermentation of glutamate by Acidaminococcus fermentans is a reversible syn-elimination of water from (R)-2-hydroxyglutaryl-CoA to (E)-glutaconyl-CoA catalyzed by 2-hydroxyglutaryl-CoA dehydratase, a two-component enzyme system. The actual dehydration is mediated by component D, which contains 1.0 [4Fe-4S](2+) cluster, 1.0 reduced riboflavin-5'-phosphate and about 0.1 molybdenum (VI) per heterodimer. The enzyme has to be activated by the extremely oxygen-sensitive [4Fe-4S](1+/2+)-cluster-containing homodimeric component A, which generates Mo(V) by an ATP/Mg2+-induced one-electron transfer. Previous experiments established that the hydroquinone state of a flavodoxin (m=14.6 kDa) isolated from A. fermentans served as one-electron donor of component A, whereby the blue semiquinone is formed. Here we describe the isolation and characterization of an alternative electron donor from the same organism, a two [4Fe-4S](1+/2+)-cluster-containing ferredoxin (m=5.6 kDa) closely related to that from Clostridium acidiurici. The protein was purified to homogeneity and almost completely sequenced; the magnetically interacting [4Fe-4S] clusters were characterized by EPR and Mossbauer spectroscopy. The redox potentials of the ferredoxin were determined as -405 mV and -340 mV. Growth experiments with A. fermentans in the presence of different iron concentrations in the medium (7-45 muM) showed that flavodoxin is the dominant electron donor protein under iron-limiting conditions. Its concentration continuously decreased from 3.5 mumol/g. protein at 7 muM Fe to 0.02 mumol/g at 45 muM Fe. In contrast, the concentration of ferredoxin increased stepwise from about 0.2 mumol/g at 7-13 muM Fe to 1.1+/-0.1 mumol/g at 17-45 muM Fe.

Harvard Citation style: Thamer, W., Cirpus, I., Hans, M., Pierik, A., Selmer, T., Bill, E., et al. (2003) A two [4Fe-4S]-cluster-containing ferredoxin as an alternative electron donor for 2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans, Archives of Microbiology, 179(3), pp. 197-204. https://doi.org/10.1007/s00203-003-0517-8

APA Citation style: Thamer, W., Cirpus, I., Hans, M., Pierik, A., Selmer, T., Bill, E., Linder, D., & Buckel, W. (2003). A two [4Fe-4S]-cluster-containing ferredoxin as an alternative electron donor for 2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans. Archives of Microbiology. 179(3), 197-204. https://doi.org/10.1007/s00203-003-0517-8