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CO synthesized from the central one-carbon pool as source for the iron carbonyl in O-2-tolerant [NiFe]-hydrogenase
Citation key ISI:000390044900060
Author Buerstel, Ingmar and Siebert, Elisabeth and Frielingsdorf, Stefan and Zebger, Ingo and Friedrich, Baerbel and Lenz, Oliver
Pages 14722-14726
Year 2016
ISSN 0027-8424
DOI 10.1073/pnas.1614656113
Address 2101 CONSTITUTION AVE NW, WASHINGTON, DC 20418 USA
Journal PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 113
Number 51
Month DEC 20
Publisher NATL ACAD SCIENCES
Abstract Hydrogenases are nature's key catalysts involved in both microbial consumption and production of molecular hydrogen. H-2 exhibits a strongly bonded, almost inert electron pair and requires transition metals for activation. Consequently, all hydrogenases are metal-loenzymes that contain at least one iron atom in the catalytic center. For appropriate interaction with H-2, the iron moiety demands for a sophisticated coordination environment that cannot be provided just by standard amino acids. This dilemma has been overcome by the introduction of unprecedented chemistry-that is, by ligating the iron with carbon monoxide (CO) and cyanide (or equivalent) groups. These ligands are both unprecedented in microbial metabolism and, in their free form, highly toxic to living organisms. Therefore, the formation of the diatomic ligands relies on dedicated biosynthesis pathways. So far, biosynthesis of the CO ligand in [NiFe]-hydrogenases was unknown. Here we show that the aerobic H-2 oxidizer Ralstonia eutropha, which produces active [NiFe]-hydrogenases in the presence of O-2, employs the auxiliary protein HypX (hydrogenase pleiotropic maturation X) for CO ligand formation. Using genetic engineering and isotope labeling experiments in combination with infrared spectroscopic investigations, we demonstrate that the alpha-carbon of glycine ends up in the CO ligand of [NiFe]-hydrogenase. The alpha-carbon of glycine is a building block of the central one-carbon metabolism intermediate, N-10-formyl-tetrahydrofolate (N-10-CHO-THF). Evidence is presented that the multidomain protein, HypX, converts the formyl group of N-10-CHO-THF into water and CO, thereby providing the carbonyl ligand for hydrogenase. This study contributes insights into microbial biosynthesis of metal carbonyls involving toxic intermediates.
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