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Structural insight into metallocofactor maturation in carbon monoxide dehydrogenase

Abstract : The nickel-dependent carbon monoxide dehydrogenase (CODH) employs a unique heterometallic Ni-Fe-S 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 Å 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 (Feu) 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 Fe-S 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 Feu 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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Submitted on : Thursday, July 18, 2019 - 3:07:55 PM
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Elizabeth Wittenborn, Steven E Cohen, Meriem Merrouch, Christophe Léger, Vincent Fourmond, et al.. Structural insight into metallocofactor maturation in carbon monoxide dehydrogenase. Journal of Biological Chemistry, American Society for Biochemistry and Molecular Biology, In press, pp.jbc.RA119.009610. ⟨10.1074/jbc.RA119.009610⟩. ⟨hal-02188452⟩



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