X-ray absorption spectroscopy of the corrinoid/iron-sulfur potein involved in acetyl coenzyme A synthesis by Clostridium thermoaceticum
- Yeshiva Univ., Bronx, NY (United States)
- Univ. of Nebraska, Lincoln (United States)
The corrinoid/iron-sulfur protein (C/Fe-SP) from Clostridium thermoaceticum is an 88 kDa [alpha][beta]-dimer that cycles between a Co(I) and methyl-Co(III) form as it transfers a methyl group from methyltetrahydrofolate (methyl-H[sub 4]folate) to carbon monoxide dehydrogenase. Extended X-ray absorption fine structure (EXAFS) and X-ray edge spectroscopy of the as-isolated C/Fe-SP indicates that the inactive Co(II) state of the corrinoid has a four-coordinate distorted square-planar structure. To the authors' knowledge, this is the first observation of a four-coordinate Co(II) corrinoid. This unusual coordination state would be expected to poise the Co(II) state of the C/Fe-SP for facile reduction to four-coordinate Co(I), which is the active nucleophile that acts as the acceptor of the methyl group of methyl-H[sub 4]folate. Additionally, the first-derivative X-ray edge spectra for both the methyl-Co(III) and Co(II) forms of the C/Fe-SP show an unexpected shift to lower energy when compared to analogous free cobalamins indicating a potential role for the protein in mediating electronic as well as structural properties of the enzyme bound methylcobamide. 42 refs., 6 figs., 3 tabs.
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 5981186
- Journal Information:
- Journal of the American Chemical Society; (United States), Vol. 115:6; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
Similar Records
Time-resolved X-ray spectroscopy of photoreduced base-off Cob(II)alamin compared to the Co(II) species in Clostridium thermoaceticum
Mechanistic enzymology of CO dehydrogenase from Clostridium thermoaceticum. Progress report, August 15, 1993--March 24, 1995
Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
COENZYMES
BIOSYNTHESIS
PROTEINS
ABSORPTION SPECTROSCOPY
X-RAY SPECTROSCOPY
CLOSTRIDIUM
COBALT COMPLEXES
EXPERIMENTAL DATA
MOLECULAR STRUCTURE
BACTERIA
COMPLEXES
DATA
INFORMATION
MICROORGANISMS
NUMERICAL DATA
ORGANIC COMPOUNDS
SPECTROSCOPY
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
550200* - Biochemistry
400102 - Chemical & Spectral Procedures