title: Recombinant expression of molybdenum reductase fragments of plant nitrate reductase at high levels in Pichia pastoris.
abstract: Mo reductase (MoR; formerly cytochrome c reductase) fragments of NADH:NO(3) reductase (NR; EC1.6.6.1) were cytosolically expressed in Pichia pastoris, a methylotrophic yeast, using spinach (Spinacia oleracea) and corn (Zea maize) cDNAs. In fermenter cultures, spinach MoR was expressed at 420 mg L(-1), corn MoR at 32 mg L(-1), and corn MoR plus with putative NR interface domain N terminus (MoR+) at 17 mg L(-1). Constitutively expressed MoR+ was structurally stable while it was degraded when expressed by methanol induction, which suggests methanol growth produces more proteinase. Methanol-induced expression yielded more target protein. All three MoR were purified to homogeneity and their polypeptides were approximately 41 (MoR) and approximately 66 (MoR+) kD. MoR was monomeric and MoR+ dimeric, confirming the predicted role for dimer interface domain of NR. MoR+, although differing in quaternary structure from MoR, has similar kinetic properties for ferricyanide and cytochrome c reductase activities and visible spectra, which were like NR. Redox potentials of MoR and MoR+ were similar for flavin, whereas MoR+ had a more negative potential for heme-iron. Reaction schemes for MoR catalyzed reactions were proposed based on fast-reaction rapid-scan stopped-flow kinetic analysis of MoR. P. pastoris is an excellent system for producing the large amounts of NR fragments needed for detailed biochemical studies.
authors.affiliation: Department of Biological Sciences and Phytotechnology Research Center, Michigan Technological University, Houghton 49931, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Mertens
authors.forename: N
authors.initials: N
authors.lastname: Shiraishi
authors.forename: W H
authors.initials: WH
authors.lastname: Campbell
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D009097:Multienzyme Complexes / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000235:genetics*; D010084:Oxidation-Reduction; D010843:Pichia / Q000201:enzymology / Q000235:genetics*; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D018724:Spinacia oleracea / Q000201:enzymology*
chemical_list: D009097:Multienzyme Complexes; D011994:Recombinant Proteins; D000445:Aldehyde Oxidoreductases; C019823:carbon monoxide dehydrogenase; D009565:Nitrate Reductases; D050901:Nitrate Reductase