title: X-ray structure of Galdieria Rubisco complexed with one sulfate ion per active site.
abstract: Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the reactions of carboxylation and oxygenation of ribulose-1,5-bisphosphate. These reactions require that the active site should be closed by a flexible loop (loop 6) of the large subunit. Rubisco from a red alga, Galdieria partita, has the highest specificity for carboxylation reaction among the Rubiscos hitherto reported. The crystal structure of unactivated Galdieria Rubisco has been determined at 2.6 A resolution. The electron density map reveals that a sulfate binds only to the P1 anion-binding site of the active site and the loop 6 is closed. Galdieria Rubisco has a unique hydrogen bond between the main chain oxygen of Val332 on the loop 6 and the epsilon-amino group of Gln386 of the same large subunit. This interaction is likely to be crucial to understanding for stabilizing the loop 6 in the closed state and to making a higher affinity for anionic ligands.
authors.affiliation: Department of Materials Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka, 565-0871, Japan.
authors.forename: Yousuke
authors.initials: Y
authors.lastname: Okano
authors.forename: Eiichi
authors.initials: E
authors.lastname: Mizohata
authors.forename: Yong
authors.initials: Y
authors.lastname: Xie
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Matsumura
authors.forename: Hajime
authors.initials: H
authors.lastname: Sugawara
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Inoue
authors.forename: Akiho
authors.initials: A
authors.lastname: Yokota
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kai
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D007477:Ions; D008958:Models, Molecular; D011487:Protein Conformation; D000461:Rhodophyta / Q000737:chemistry*; D012273:Ribulose-Bisphosphate Carboxylase / Q000737:chemistry* / Q000378:metabolism*; D013431:Sulfates / Q000378:metabolism*
chemical_list: D007477:Ions; D013431:Sulfates; D012273:Ribulose-Bisphosphate Carboxylase