title: Structure of rabbit muscle pyruvate kinase complexed with Mn2+, K+, and pyruvate.
abstract: The molecular structure of rabbit muscle pyruvate kinase, crystallized as a complex with Mn2+, K+, and pyruvate, has been solved to 2.9-A resolution. Crystals employed in the investigation belonged to the space group P1 and had unit cell dimensions a = 83.6 A, b = 109.9 A, c = 146.8 A, alpha = 94.9 degrees, beta = 93.6 degrees, and gamma = 112.3 degrees. There were two tetramers in the asymmetric unit. The structure was solved by molecular replacement, using as the search model the coordinates of the tetramer of pyruvate kinase from cat muscle [Muirhead, H., Claydon, D. A., Barford, D., Lorimer, C. G., Fothergill-Gilmore, L. A., Schiltz, E., & Schmitt, W. (1986) EMBO J.5, 475-481]. The amino acid sequence derived from the cDNA coding for the enzyme from rabbit muscle was fit to the electron density. The rabbit and cat muscle enzymes have approximately 94% sequence identity, and the folding patterns are expected to be nearly identical. There are, however, three regions where the topological models of the cat and rabbit pyruvate kinases differ. Mn2+ coordinates to the protein through the carboxylate side chains of Glu 271 and Asp 295. These two residues are strictly conserved in all known pyruvate kinases. In addition, the density for Mn2+ is connected to that of pyruvate, consistent with chelation through a carboxylate oxygen and the carbonyl oxygen of the substrate. The epsilon-NH2 of Lys 269 and the OH of Thr 327 lie on either side of the methyl group of bound pyruvate. Spherical electron density, assigned to K+, is located within a well-defined pocket of four oxygen ligands contributed by the carbonyl oxygen of Thr 113, O gamma of Ser 76, O delta 1 of Asn 74, and O delta 2 of Asp 112. The interaction of Asp 112 with the side chains of Lys 269 and Arg 72 may mediate, indirectly, monovalent cation effects on activity.
authors.affiliation: Institute for Enzyme Research, Graduate School, University of Wisconsin-Madison 53705.
authors.forename: T M
authors.initials: TM
authors.lastname: Larsen
authors.forename: L T
authors.initials: LT
authors.lastname: Laughlin
authors.forename: H M
authors.initials: HM
authors.lastname: Holden
authors.forename: I
authors.initials: I
authors.lastname: Rayment
authors.forename: G H
authors.initials: GH
authors.lastname: Reed
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002412:Cations; D003460:Crystallization; D018360:Crystallography, X-Ray; D046911:Macromolecular Substances; D008345:Manganese / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009132:Muscles / Q000201:enzymology*; D011188:Potassium / Q000378:metabolism*; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011770:Pyruvate Kinase / Q000737:chemistry* / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism*; D019289:Pyruvic Acid; D011817:Rabbits; D051381:Rats; D017385:Sequence Homology
chemical_list: D002412:Cations; D046911:Macromolecular Substances; D011773:Pyruvates; D008345:Manganese; D019289:Pyruvic Acid; D011770:Pyruvate Kinase; D011188:Potassium