title: Stoichiometry of ATP hydrolysis and chlorophyllide formation of dark-operative protochlorophyllide oxidoreductase from Rhodobacter capsulatus.
abstract: Dark-operative protochlorophyllide (Pchlide) oxidoreductase (DPOR) is a nitrogenase-like enzyme catalyzing a reduction of the C17 = C18 double bond of Pchlide to form chlorophyllide a (Chlide) in bacteriochlorophyll biosynthesis. DPOR consists of an ATP-dependent reductase component, L-protein (a BchL dimer), and a catalytic component, NB-protein (a BchN-BchB heterotetramer). The L-protein transfers electrons to the NB-protein to reduce Pchlide, which is coupled with ATP hydrolysis. Here we determined the stoichiometry of ATP hydrolysis and the Chlide formation of DPOR. The minimal ratio of ATP to Chlide (ATP/2e(-)) was 4, which coincides with that of nitrogenase. The ratio increases with increasing molar ratio of L-protein to NB-protein. This profile differs from that of nitrogenase. These results suggest that DPOR has a specific intrinsic property, while retaining the common features shared with nitrogenase.
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan.
authors.forename: Jiro
authors.initials: J
authors.lastname: Nomata
authors.affiliation: Department of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Terauchi
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan. Electronic address: fujita@agr.nagoya-u.ac.jp.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Fujita
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry* / Q000528:radiation effects; D002735:Chlorophyllides / Q000737:chemistry* / Q000528:radiation effects; D006868:Hydrolysis; D008027:Light; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000737:chemistry* / Q000528:radiation effects; D016354:Rhodobacter capsulatus / Q000201:enzymology* / Q000528:radiation effects
chemical_list: D002735:Chlorophyllides; D000255:Adenosine Triphosphate; D044925:Oxidoreductases Acting on CH-CH Group Donors; C023886:protochlorophyllide reductase
keywords: ATPase; BchL; Dark-operative protochlorophyllide oxidoreductase; L-protein; Nitrogenase; Rhodobacter capsulatus