title: Formation of functional heterodimers by isozymes 1 and 2 of pyruvate dehydrogenase kinase.
abstract: Pyruvate dehydrogenase kinase (PDK) is a mitochondrial enzyme responsible for regulation of the pyruvate dehydrogenase complex and, consequently, aerobic oxidation of carbohydrate fuels in general. In mammals, there are four genetically and biochemically distinct forms of PDK that are expressed in a tissue-specific manner (PDK1, PDK2, PDK3, and PDK4). These protein kinases have been shown to function as dimers, but the possibility of heterodimerization between various isozyme subunits has not yet been investigated. Here, we demonstrate that two members of the PDK family, PDK1 and PDK2, form heterodimeric species when coexpressed in the same Escherichia coli cell. The heterodimeric kinase produced in vivo was purified to near homogeneity by affinity chromatography. The purified kinase was stable and was not subjected to reassortment of the subunits. The heterodimeric kinase was catalytically active and was clearly distinct from homodimeric PDK1 or PDK2 with respect to kinetic parameters, site specificity and regulation. These data strongly suggest that heterodimerization between PDK1 and PDK2 adds another level of diversity to this protein family in addition to that which arises from gene multiplicity.
authors.affiliation: Division of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City, 5110 Rockhill Road, Kansas City, MO 64110-2499, USA.
authors.forename: Igor
authors.initials: I
authors.lastname: Boulatnikov
authors.forename: Kirill M
authors.initials: KM
authors.lastname: Popov
mesh_terms: D000818:Animals; D002846:Chromatography, Affinity; D019281:Dimerization; D004926:Escherichia coli / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D007527:Isoenzymes / Q000235:genetics; D007700:Kinetics; D008929:Mitochondria, Heart / Q000201:enzymology; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D020836:Protein Structure, Quaternary; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D011768:Pyruvate Dehydrogenase Complex / Q000235:genetics / Q000378:metabolism; D051381:Rats
chemical_list: D007527:Isoenzymes; C000631434:Pdk1 protein, rat; C000631436:Pdk2 protein, rat; C000631438:Pdk3 protein, rat; C000631440:Pdk4 protein, rat; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D011768:Pyruvate Dehydrogenase Complex; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases