The crystal structure of C176A mutated [Fe]‐hydrogenase suggests an acyl‐iron ligation in the active site iron complex

Abstract

a b s t r a c t[Fe]-hydrogenase is one of three types of enzymes known to activate H 2 . Crystal structure analysis recently revealed that its active site iron is ligated square-pyramidally by Cys176-sulfur, two CO, an ''unknown" ligand and the sp 2 -hybridized nitrogen of a unique iron-guanylylpyridinol-cofactor. We report here on the structure of the C176A mutated enzyme crystallized in the presence of dithiothreitol (DTT). It suggests an iron center octahedrally coordinated by one DTT-sulfur and one DTToxygen, two CO, the 2-pyridinol's nitrogen and the 2-pyridinol's 6-formylmethyl group in an acyliron ligation. This result led to a re-interpretation of the iron ligation in the wild-type.

A glycyl free radical as the precursor in the synthesis of carbon monoxide and cyanide by the [FeFe]‐hydrogenase maturase HydG

“…Because of the complexity of hydrogenases' active sites ( Fig. 1), they require maturation machineries that involve metal ion transport, synthesis of CN À and/or CO, formation and insertion of a FeCO(CN À ) 2 , Fe 2 (CO) 2 (CN À ) 2 or Fe(CO) 2 unit to the apo enzyme, synthesis of a complex nucleotide cofactor ([Fe]-hydrogenase), a di-(thiomethyl)amine molecule ([FeFe]-hydrogenase) or insertion of nickel and proteolytic cleavage of a C-terminal stretch ([NiFe]-hydrogenase) [1][2][3]. Since the active sites of the latter two enzymes are buried in the structure, electron and proton transfer pathways and gas tunnels are required to communicate between these sites and the molecular surface [4].…”

Protein-pyridinol thioester precursor for biosynthesis of the organometallic acyl-iron ligand in [Fe]-hydrogenase cofactor

“…N ature expands the catalytic capability of proteins by developing metal cofactors 1 [Fe]-hydrogenase has a guanylylpyridinol (GP), which is bidentately chelated to Fe by its nitrogen and acyl-carbon 6,7 . The Fe-acyl bond constitutes the only stable acyl-organometallic compound found in nature, although an acyl-Ni species has been reported to be an intermediate in the acetyl-CoA formation reaction catalysed by acetyl-CoA synthase 8,9 .…”

Theoretical 57Fe Mössbauer spectroscopy: isomer shifts of [Fe]-hydrogenase intermediates

“…To this end, we selected the recently characterized [Fe]-hydrogenase [28][29][30] which stands out from other classes of hydrogenases as it contains no iron-sulfur clusters as well as only a mono-nuclear metal site. Mössbauer studies on [Fe]-hydrogenase have been carried out by Shima et al 31 In this paper we use the correlation plots from molecules 1-5 to calculate isomer shifts for the [Fe]-hydrogenase intermediates.…”