RESUMEN
Formation of the catalytic six-iron complex (H-cluster) of [FeFe]-hydrogenase (HydA) requires its interaction with a specific maturation protein, HydF. Comparison by X-ray absorption spectroscopy at the Fe K-edge of HydF from Clostridium acetobutylicum and HydA1 from Chlamydomonas reinhardtii revealed that the overall structure of the iron site in both proteins is highly similar, comprising a [4Fe4S] cluster (Fe-Fe distances of â¼2.7Å) and a di-iron unit (Fe-Fe distance of â¼2.5Å). Thus, a precursor of the whole H-cluster is assembled on HydF. Formation of the core structures of both the 4Fe and 2Fe units may require only the housekeeping [FeS] cluster assembly machinery of the cell. Presumably, only the 2Fe cluster is transferred from HydF to HydA1, thereby forming the active site.
Asunto(s)
Proteínas Bacterianas/metabolismo , Chlamydomonas reinhardtii/enzimología , Clostridium acetobutylicum/enzimología , Hidrogenasas/metabolismo , Proteínas Hierro-Azufre/metabolismo , Proteínas Bacterianas/química , Sitios de Unión , Hidrógeno/química , Hidrógeno/metabolismo , Hidrogenasas/química , Hierro/química , Hierro/metabolismo , Proteínas Hierro-Azufre/química , Unión Proteica , Espectroscopía de Absorción de Rayos X/métodosRESUMEN
Biosynthesis of the [FeFe] hydrogenases active site (H-cluster) requires three maturation factors whose respective roles are not understood yet. The clostridial maturation enzymes (CaHydE, CaHydF and CaHydG) were homologously overexpressed in their native host Clostridium acetobutylicum. CaHydF was able to activate Chlamydomonas reinhardtii [FeFe] hydrogenase apoprotein (CrHydA1(apo)) to almost 100% compared to the native specific hydrogen evolution activity. Based on electron paramagnetic resonance spectroscopy and Fourier-transform infrared spectroscopy data the existence of a [4Fe4S] cluster and a CO and CN(-) ligand coordinated di-iron cluster is suggested. This study contains the first experimental evidence that the bi-nuclear part of the H-cluster is assembled in HydF.