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Probing the origin of the metabolic precursor of the CO ligand in the catalytic center of [NiFe]-hydrogenase.
Zitatschlüssel Burstel2011
Autor Ingmar Burstel and Philipp Hummel and Elisabeth Siebert and Nattawadee Wisitruangsakul and Ingo Zebger and Barbel Friedrich and Oliver Lenz
Jahr 2011
DOI 10.1074/jbc.M111.309351
Journal J Biol Chem
Monat Nov
Zusammenfassung The O(2)-tolerant [NiFe]-hydrogenases of Ralstonia eutropha are capable of H(2) conversion in the presence of ambient O(2). Oxygen represents not only a challenge for catalysis but also for the complex assembling process of the [NiFe]-active site. Apart from nickel and iron, the catalyic center contains unusual diatomic ligands, namely two cyanides (CN(-)) and one carbon monoxide (CO), which are coordinated to the iron. One of the open questions of the maturation process concerns the origin and biosynthesis of the CO group. Isotope labeling in combination with infrared spectroscopy revealed that externally supplied gaseous (13)CO serves as precursor of the carbonyl group of the regulatory [NiFe]-hydrogenase (RH) in R. eutropha. Corresponding (13)CO titration experiments showed that a concentration 130-fold higher than ambient CO (0.1 ppmv) caused a fifty percent labeling of the carbonyl ligand in the RH, leading to the conclusion that the carbonyl ligand originates from an intracellular metabolite. A novel setup allowed us to study effects of CO depletion on maturation in vivo. Upon induction of CO depletion by addition of the CO scavenger PdCl(2), cells cultivated on H(2), CO(2) and O(2) showed severe growth retardation at low cell concentrations, which was based on partially arrested hydrogenase maturation leading to reduced hydrogenase activity. This suggests gaseous CO as metabolic precursor under these conditions. The addition of PdCl(2) to cells cultivated heterotrophically on organic substrates had no effect on hydrogenase maturation. These results indicate at least two different pathways for biosynthesis of the CO ligand of [NiFe]-hydrogenase.
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