TY  - JOUR
A1  - Schrapers, Peer
A1  - Hartmann, Tobias
A1  - Kositzki, Ramona
A1  - Dau, Holger
A1  - Reschke, Stefan
A1  - Schulzke, Carola
A1  - Leimkühler, Silke
A1  - Haumann, Michael
T1  - 'Sulfido and Cysteine Ligation Changes at the Molybdenum Cofactor during Substrate Conversion by Formate Dehydrogenase (FDH) from Rhodobacter capsulatus
T2  - Inorganic chemistry
N2  - Formate dehydrogenase (FDH) enzymes are attractive catalysts for potential carbon dioxide conversion applications. The FDH from Rhodobacter capsulatus (RcFDH) binds a bis-molybdopterin-guanine-dinucleotide (bis-MGD) cofactor, facilitating reversible formate (HCOO-) to CO2 oxidation. We characterized the molecular structure of the active site of wildtype RcFDH and protein variants using X-ray absorption spectroscopy (XAS) at the Mo K-edge. This approach has revealed concomitant binding of a sulfido ligand (Mo=S) and a conserved cysteine residue (S(Cys386)) to Mo(VI) in the active oxidized molybdenum cofactor (Moco), retention of such a coordination motif at Mo(V) in a chemically reduced enzyme, and replacement of only the S(Cys386) ligand by an oxygen of formate upon Mo(IV) formation. The lack of a Mo=S bond in RcFDH expressed in the absence of FdsC implies specific metal sulfuration by this bis-MGD binding chaperone. This process still functioned in the Cys386Ser variant, showing no Mo-S(Cys386) ligand, but retaining a Mo=S bond. The C386S variant and the protein expressed without FdsC were inactive in formate oxidation, supporting that both Moligands are essential for catalysis. Low-pH inhibition of RcFDH was attributed to protonation at the conserved His387, supported by the enhanced activity of the His387Met variant at low pH, whereas inactive cofactor species showed sulfido-to-oxo group exchange at the Mo ion. Our results support that the sulfido and S(Cys386) ligands at Mo and a hydrogen-bonded network including His387 are crucial for positioning, deprotonation, and oxidation of formate during the reaction cycle of RcFDH.
Y1  - 2015
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/39010
SN  - 0020-1669
SN  - 1520-510X
VL  - 54
IS  - 7
SP  - 3260
EP  - 3271
PB  - American Chemical Society
CY  - Washington
ER  -