X-ray absorption spectroscopy of the corrinoid/iron-sulfur potein involved in acetyl coenzyme A synthesis by Clostridium thermoaceticum

Journal Article · Tue Mar 23 23:00:00 EST 1993 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00059a007· OSTI ID:5981186

Wirt, M D; Chance, M R ^[1]; Kumar, M; Ragsdale, S W ^[2]

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1. Yeshiva Univ., Bronx, NY (United States)
2. 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), Journal Name: Journal of the American Chemical Society; (United States) Vol. 115:6; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ABSORPTION SPECTROSCOPY
BACTERIA
BIOSYNTHESIS
CLOSTRIDIUM
COBALT COMPLEXES
COENZYMES
COMPLEXES
DATA
EXPERIMENTAL DATA
INFORMATION
MICROORGANISMS
MOLECULAR STRUCTURE
NUMERICAL DATA
ORGANIC COMPOUNDS
PROTEINS
SPECTROSCOPY
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
X-RAY SPECTROSCOPY