title: NiFe hydrogenase active site biosynthesis: identification of Hyp protein complexes in Ralstonia eutropha.
abstract: Biosynthesis of the NiFe hydrogenase active site is a complex process involving the action of the Hyp proteins: HypA-HypF. Here we investigate the mechanism of NiFe site biosynthesis in Ralstonia eutropha by examining the interactions between HypC, HypD, HypE, and HypF1. Using an affinity purification procedure based on the Strep-tag II, we purified HypC and HypE from different genetic backgrounds as complexes with other hydrogenase-related proteins and characterized them using immunological analysis. Copurification of HypC and HoxH, the active site-containing subunit of the soluble hydrogenase in R. eutropha, from several different genetic backgrounds suggests that this complex forms early in the maturation process. With respect to the Hyp proteins, it is shown that HypE and HypF1 formed a stable complex both in vivo and in vitro. Furthermore, HypC and HypD functioned as a unit. Together, they were able to interact with HypE to form a range of complexes probably varying in stoichiometry. The HypC/HypD/HypE complexes did not involve HypF1 but appeared to be more stable when HypF1 was also present in the cells. We hypothesize that HypF1 is able to modify some component of the HypC/HypD/HypE complex. Since we have also seen that HypF1 and HypE form a complex, it is likely that HypF1 modifies HypE. On the basis of these results, we propose a complete catalytic cycle for HypE. First, it is modified by HypF1, and then it can form a complex with HypC/HypD. This activated HypE/HypC/HypD complex could then decompose by donating active site components to the immature hydrogenase and regenerate unmodified HypE.
authors.affiliation: Institut für Biologie, Humboldt-Universität zu Berlin, 10115 Berlin, Germany.
authors.forename: Anne K
authors.initials: AK
authors.lastname: Jones
authors.forename: Oliver
authors.initials: O
authors.lastname: Lenz
authors.forename: Angelika
authors.initials: A
authors.lastname: Strack
authors.forename: Thorsten
authors.initials: T
authors.lastname: Buhrke
authors.forename: Bärbel
authors.initials: B
authors.lastname: Friedrich
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification*; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D020118:Cupriavidus necator / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D005782:Gels; D017353:Gene Deletion; D005816:Genetic Complementation Test; D006864:Hydrogenase / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D007501:Iron / Q000737:chemistry; D046911:Macromolecular Substances; D008970:Molecular Weight; D009532:Nickel / Q000737:chemistry; D011489:Protein Denaturation; D011506:Proteins / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D000180:Acrylic Resins; D001426:Bacterial Proteins; D005782:Gels; C108874:HypC protein, Bacteria; C108875:HypD protein, Bacteria; C108878:HypF protein, Bacteria; D046911:Macromolecular Substances; D011506:Proteins; C085871:hypE protein, Bacteria; C016680:polyacrylamide gels; D009532:Nickel; D007501:Iron; C043296:nickel-iron hydrogenase; D006864:Hydrogenase