1a3x
PYRUVATE KINASE FROM SACCHAROMYCES CEREVISIAE COMPLEXED WITH PG, MN2+ AND K+
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OverviewOverview
BACKGROUND: Yeast pyruvate kinase (PK) catalyzes the final step in, glycolysis. The enzyme therefore represents an important control point and, is allosterically activated by fructose-1,6-bisphosphate (FBP). In mammals, the enzyme is found as four different isozymes with different regulatory, properties: two of these isozymes are produced by alternate splicing. The, allosteric regulation of PK is directly related to proliferation of, certain cell types, as demonstrated by the expression of an allosterically, regulated isozyme in tumor cells. A model for the allosteric transition, from the inactive (T) state to the active (R) state has been proposed, previously, but until now the FBP-binding site had not been identified., RESULTS: We report here the structures of PK from yeast complexed with a, substrate analog and catalytic metal ions in the presence and absence of, bound FBP. The allosteric site is located 40 A from the active site and is, entirely located in the enzyme regulatory (C) domain. A phosphate-binding, site for the allosteric activator is created by residues encoded by a, region of the gene corresponding to the alternately spliced exon of, mammalian isozymes. FBP activation appears to induce several, conformational changes among active-site sidechains through a mechanism, that is most likely to involve significant domain motions, as previously, hypothesized. CONCLUSIONS: The structure and location of the allosteric, activator site agrees with the pattern of alternate genetic splicing of, the PK gene in multicellular eukaryotes that distinguishes between a, non-regulated isozyme and the regulated fetal isozymes. The conformational, differences observed between the active sites of inactive and fully active, PK enzymes is in agreement with the recently determined thermodynamic, mechanism of allosteric activation through a 'metal relay' that increases, the affinity of the enzyme for its natural phosphoenolpyruvate substrate.
About this StructureAbout this Structure
1A3X is a Single protein structure of sequence from Saccharomyces cerevisiae with PGA, MN and K as ligands. Active as Pyruvate kinase, with EC number 2.7.1.40 Full crystallographic information is available from OCA.
ReferenceReference
The allosteric regulation of pyruvate kinase by fructose-1,6-bisphosphate., Jurica MS, Mesecar A, Heath PJ, Shi W, Nowak T, Stoddard BL, Structure. 1998 Feb 15;6(2):195-210. PMID:9519410
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