期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 294, 期 35, 页码 13017-13026出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.RA119.009610
关键词
nickel; iron-sulfur protein; metalloenzyme; one-carbon metabolism; oxidation-reduction (redox); X-ray crystallography; bioremediation catalyst; carbon monoxide dehydrogenase (CODH); heterometallic cofactor
资金
- National Institutes of Health [T32 GM008334, R01 GM069857, R35 GM126982]
- French Agence Nationale de la Recherche [ANR-15-CE05-0020, ANR-17-CE11-0027]
- Agence Nationale de la Recherche (ANR) [ANR-17-CE11-0027] Funding Source: Agence Nationale de la Recherche (ANR)
The nickel-dependent carbon monoxide dehydrogenase (CODH) employs a unique heterometallic nickel-iron-sulfur cluster, termed the C-cluster, to catalyze the interconversion of CO and CO2. Like other complex metalloenzymes, CODH requires dedicated assembly machinery to form the fully intact and functional C-cluster. In particular, nickel incorporation into the C-cluster depends on the maturation factor CooC; however, the mechanism of nickel insertion remains poorly understood. Here, we compare X-ray structures (1.50-2.48 angstrom resolution) of CODH from Desulfovibrio vulgaris (DvCODH) heterologously expressed in either the absence (DvCODH(-CooC)) or presence (DvCODH(+CooC)) of co-expressed CooC. We find that the C-cluster of DvCODH(-CooC) is fully loaded with iron but does not contain any nickel. Interestingly, the so-called unique iron ion (Fe-u) occupies both its canonical site (80% occupancy) and the nickel site (20% occupancy), with addition of reductant causing further mismetallation of the nickel site (60% iron occupancy). We also demonstrate that a DvCODH variant that lacks a surface-accessible iron-sulfur cluster (the D-cluster) has a C-cluster that is also replete in iron but lacks nickel, despite co-expression with CooC. In this variant, all Fe-u is in its canonical location, and the nickel site is empty. This D-cluster-deficient CODH is inactive despite attempts to reconstitute it with nickel. Taken together, these results suggest that an empty nickel site is not sufficient for nickel incorporation. Based on our findings, we propose a model for C-cluster assembly that requires both CooC and a functioning D-cluster, involves precise redox-state control, and includes a two-step nickel-binding process.
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