title: Crystal structure of the ternary complex of ribulose-1,5-bisphosphate carboxylase, Mg(II), and activator CO2 at 2.3-A resolution.
abstract: The activated ternary complex, enzyme-CO2-Mg(II), of the dimeric ribulose-1,5-bisphosphate carboxylase/oxygenase from Rhodospirillum rubrum can be prepared in the same crystal form that was used for the crystallographic structure determination of the native nonactivated enzyme (Schneider, G., Bränden, C.-I., & Lorimer, G. (1986) J. Mol. Biol. 187, 141-143). The three-dimensional structure of the activated enzyme has been determined to a nominal resolution of 2.3 A by protein crystallographic methods. The activator CO2 forms a carbamate with Lys191, located at the bottom of the funnel-shaped active site. In both subunits, this labile adduct is stabilized by a Mg(II) ion, bound to the carbamate and the side chains of Asp193 and Glu194. One solvent molecule was found within the first coordination sphere of the metal ion. The metal-binding site in ribulose-1,5-bisphosphate carboxylase consists thus of at least three protein ligands, all located on loop 2 of the beta/alpha barrel. One additional metal ligand, the side chain of the conserved Asn111, was observed close to the Mg(II) ion in the B-subunit. Other structural differences at the active site between the activated and nonactivated enzyme are limited to side-chain positions. Nevertheless, it is obvious that the hydrogen-bonding pattern in the vicinity of the activator site is completely altered.
authors.affiliation: Department of Molecular Biology, Swedish University of Agricultural Sciences, Uppsala.
authors.forename: T
authors.initials: T
authors.lastname: Lundqvist
authors.forename: G
authors.initials: G
authors.lastname: Schneider
mesh_terms: D001665:Binding Sites; D002219:Carbamates / Q000378:metabolism; D002245:Carbon Dioxide / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D004795:Enzyme Stability / Q000187:drug effects; D006860:Hydrogen Bonding; D008274:Magnesium / Q000494:pharmacology*; D011487:Protein Conformation; D012247:Rhodospirillum rubrum / Q000201:enzymology; D012273:Ribulose-Bisphosphate Carboxylase / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D002219:Carbamates; D002245:Carbon Dioxide; D012273:Ribulose-Bisphosphate Carboxylase; D008274:Magnesium