Crystal Structures of [Fe]‐Hydrogenase in Complex with Inhibitory Isocyanides: Implications for the H₂‐Activation Site

Dioxygen Sensitivity of [Fe]‐Hydrogenase in the Presence of Reducing Substrates

“…Guanylylpyridinol was identified as alight-deactivated product of the isolated FeGP cofactor (Figure 1b). [7] Thei ron in the O 2 -deactivated enzyme has lost pyridinol-N,a cyl-C, and two CO ligands,b ut is still coordinated with Cys172-S,a nd [14] which is the only available crystal structure of [Fe]-hydrogenase derived from Methanothermobacter marburgensis. b) The active-site structure of the O 2 -deactivated [Fe]-hydrogenase, in which the 2 F o ÀF c electron density contoured at 3.0 s is represented (Supporting Information, Table S1).…”

5 Metal centers in hydrogenase enzymes studied by X-ray spectroscopy

“…The structure and accompanying Fe-XAS data were interpreted as showing the binding of the pyridinole ring solely via its nitrogen atom to the iron. A recent combined XAS and crystallography study has shown that isocyanide compounds bind to the iron trans to the acyl ligand and to the hydroxo group of the pyridinole ring, which is circumstantial evidence for a similar binding of H 2 [32]. In the same study, the Fe-EXAFS analysis was refined, showing the compatibility of the data also with six-coordinated iron.…”

6 Structure and function of [Fe]-hydrogenase and biosynthesis of the FeGP cofactor

“…The apoenzyme crystal structure of the enzyme from Methanocaldococcus jannaschii was solved by molecular replacement using the Methanopyrus kandleri apoenzyme structure as a search model and was refined successfully [9]. Crystals of [Fe]-hydrogenase from Methanothermobacter marburgensis, which is used for most biochemical analyses of this enzyme, were obtained only in the isocyanide -inhibited forms [12]. Crystals of [Fe]-hydrogenase from Methanothermobacter marburgensis, which is used for most biochemical analyses of this enzyme, were obtained only in the isocyanide -inhibited forms [12].…”

“…The K i of isocyanide inhibition (1-150 nM) is much lower than that of CO (0.1 mM) and CN − (0.2 mM). These inhibitory compounds appear to commonly bind to the open site of the FeGP cofactor, but why only isocyanides are much stronger inhibitors had been obscure until the crystal structure of [Fe]-hydrogenase inhibited with isocyanide was determined [12]. These inhibitory compounds appear to commonly bind to the open site of the FeGP cofactor, but why only isocyanides are much stronger inhibitors had been obscure until the crystal structure of [Fe]-hydrogenase inhibited with isocyanide was determined [12].…”

“…Infrared spectroscopic analyses indicate that binding of CO and CN − as well as of CN − and isocyanides are mutually exclusive [19]. Crystal structures of complexes of [Fe]-hydrogenase with CN − and isocyanides have been reported [10,12]. Crystal structures of complexes of [Fe]-hydrogenase with CN − and isocyanides have been reported [10,12].…”