A glycyl free radical as the precursor in the synthesis of carbon monoxide and cyanide by the [FeFe]-hydrogenase maturase HydG.
HydG uses tyrosine to synthesize the CN(-)/CO ligands of [FeFe]-hydrogenase active site. We have mutated two of the [4Fe-4S]-cluster cysteine ligands of the HydG C-terminal domain (CTD) to serine. The double mutant can still synthesize CN(-) but not CO. In a mutant lacking the CTD both CN(-) and CO synthesis are abolished. Like in ThiH, the initial steps of CN(-) synthesis are carried out in the TIM-barrel domain of HydG but some component(s) of the CTD are later needed. The mutants indicate that CO synthesis is metal-based and occurs in the CTD. We postulate that CN(-)/CO synthesis is initiated by H(2)N-*CH-CO(2)(-). Fragmentation of this radical into H(2)N-*CH(2) and CO(2) or H(2)C=NH and *CO(2)(-) provides plausible precursors for CN(-)/CO synthesis.
Nicolet
Yvain
Y
Laboratoire de Cristallographie et de Cristallogenèse des Protéines, Institut de Biologie Structurale Jean-Pierre Ebel, CEA, CNRS, Université Joseph Fourier, Grenoble, France.
Martin
Lydie
L
Tron
Cécile
C
Fontecilla-Camps
Juan C
JC
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002248:Carbon Monoxide / Q000378:metabolism; D020134:Catalytic Domain; D003001:Cloning, Molecular; D046969:Clostridium acetobutylicum / Q000201:enzymology* / Q000235:genetics; D003486:Cyanides / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D005609:Free Radicals / Q000378:metabolism; D005798:Genes, Bacterial; D006864:Hydrogenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008956:Models, Chemical; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D003486:Cyanides; D017931:DNA Primers; D005609:Free Radicals; D007506:Iron-Sulfur Proteins; D050505:Mutant Proteins; D011994:Recombinant Proteins; D002248:Carbon Monoxide; C118830:iron hydrogenase; D006864:Hydrogenase