title: Histidine mutagenesis of Arabidopsis thaliana pyruvate dehydrogenase kinase.
abstract: Pyruvate dehydrogenase kinase (PDK) is the primary regulator of flux through the mitochondrial pyruvate dehydrogenase complex (PDC). Analysis of the primary amino-acid sequences of PDK from various sources reveals that these enzymes include the five domains characteristic of prokaryotic two-component His-kinases, despite the fact that PDK exclusively phosphorylates Ser residues in the E1alpha subunit of the PDC. This seeming contradiction might be resolved if the PDK-catalyzed reaction employed a phospho-His intermediate. The results from pH-stability studies of autophosphorylated Arabidopsis thaliana PDK did not provide any support for a phospho-His intermediate. Furthermore, site-directed mutagenesis of the two most likely phosphotransfer His residues (H121 and H168) did not abolish either PDK autophosphorylation or the ability to transphosphorylate E1alpha. Thus, PDK is a unique type of protein kinase having a His-kinase-like sequence but Ser-kinase activity.
authors.affiliation: Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Tovar-Mendez
authors.forename: Jan A
authors.initials: JA
authors.lastname: Miernyk
authors.forename: Douglas D
authors.initials: DD
authors.lastname: Randall
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D006639:Histidine / Q000235:genetics*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D011994:Recombinant Proteins; D006639:Histidine; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases