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Title: X-ray Absorption Spectroscopy Reveals an Organometallic Ni–C Bond in the CO-Treated Form of Acetyl-CoA Synthase

Abstract

Acetyl-CoA synthase (ACS) is a key enzyme in the Wood–Ljungdahl pathway of anaerobic CO 2 fixation, which has long been proposed to operate by a novel mechanism involving a series of protein-bound organometallic (Ni–CO, methyl–Ni, and acetyl–Ni) intermediates. Here we report the first direct structural evidence of the proposed metal–carbon bond. We describe the preparation of the highly active metal-replete enzyme and near-quantitative generation of the kinetically competent carbonylated intermediate. This advance has allowed a combination of Ni and Fe K-edge X-ray absorption spectroscopy and extended X-ray absorption fine structure experiments along with density functional theory calculations. The data reveal that CO binds to the proximal Ni of the six-metal metallocenter at the active site and undergoes dramatic structural and electronic perturbation in forming this organometallic Ni–CO intermediate. This direct identification of a Ni–carbon bond in the catalytically competent CO-bound form of the In conclusion, a cluster of ACS provides definitive experimental structural evidence supporting the proposed organometallic mechanism of anaerobic acetyl-CoA synthesis.

Authors:
 [1];  [2]; ORCiD logo [1];  [3]
  1. Univ. of Michigan, Ann Arbor, MI (United States)
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States)
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1353212
Grant/Contract Number:
R37 GM39451; AC02-76SF00515
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Biochemistry
Additional Journal Information:
Journal Volume: 56; Journal Issue: 9; Journal ID: ISSN 0006-2960
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 59 BASIC BIOLOGICAL SCIENCES; ACS; Ni K-edge; XAS; EXAFS; Ni-Co; [Fe4S4]; EPR; Wood-Ljungdahl

Citation Formats

Can, Mehmet, Giles, Logan J., Ragsdale, Stephen W., and Sarangi, Ritimukta. X-ray Absorption Spectroscopy Reveals an Organometallic Ni–C Bond in the CO-Treated Form of Acetyl-CoA Synthase. United States: N. p., 2017. Web. doi:10.1021/acs.biochem.6b00983.
Can, Mehmet, Giles, Logan J., Ragsdale, Stephen W., & Sarangi, Ritimukta. X-ray Absorption Spectroscopy Reveals an Organometallic Ni–C Bond in the CO-Treated Form of Acetyl-CoA Synthase. United States. doi:10.1021/acs.biochem.6b00983.
Can, Mehmet, Giles, Logan J., Ragsdale, Stephen W., and Sarangi, Ritimukta. Fri . "X-ray Absorption Spectroscopy Reveals an Organometallic Ni–C Bond in the CO-Treated Form of Acetyl-CoA Synthase". United States. doi:10.1021/acs.biochem.6b00983. https://www.osti.gov/servlets/purl/1353212.
@article{osti_1353212,
title = {X-ray Absorption Spectroscopy Reveals an Organometallic Ni–C Bond in the CO-Treated Form of Acetyl-CoA Synthase},
author = {Can, Mehmet and Giles, Logan J. and Ragsdale, Stephen W. and Sarangi, Ritimukta},
abstractNote = {Acetyl-CoA synthase (ACS) is a key enzyme in the Wood–Ljungdahl pathway of anaerobic CO2 fixation, which has long been proposed to operate by a novel mechanism involving a series of protein-bound organometallic (Ni–CO, methyl–Ni, and acetyl–Ni) intermediates. Here we report the first direct structural evidence of the proposed metal–carbon bond. We describe the preparation of the highly active metal-replete enzyme and near-quantitative generation of the kinetically competent carbonylated intermediate. This advance has allowed a combination of Ni and Fe K-edge X-ray absorption spectroscopy and extended X-ray absorption fine structure experiments along with density functional theory calculations. The data reveal that CO binds to the proximal Ni of the six-metal metallocenter at the active site and undergoes dramatic structural and electronic perturbation in forming this organometallic Ni–CO intermediate. This direct identification of a Ni–carbon bond in the catalytically competent CO-bound form of the In conclusion, a cluster of ACS provides definitive experimental structural evidence supporting the proposed organometallic mechanism of anaerobic acetyl-CoA synthesis.},
doi = {10.1021/acs.biochem.6b00983},
journal = {Biochemistry},
number = 9,
volume = 56,
place = {United States},
year = {Fri Feb 10 00:00:00 EST 2017},
month = {Fri Feb 10 00:00:00 EST 2017}
}

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