Boulatnikov Igor, Popov Kirill M
Division of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City, 5110 Rockhill Road, Kansas City, MO 64110-2499, USA.
Biochim Biophys Acta. 2003 Feb 21;1645(2):183-92. doi: 10.1016/s1570-9639(02)00542-3.
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.
丙酮酸脱氢酶激酶（PDK）是一种线粒体酶，负责调节丙酮酸脱氢酶复合体，进而总体上调节碳水化合物燃料的有氧氧化。在哺乳动物中，有四种在基因和生化性质上不同的PDK形式，它们以组织特异性方式表达（PDK1、PDK2、PDK3和PDK4）。这些蛋白激酶已被证明以二聚体形式发挥作用，但尚未研究各种同工酶亚基之间异源二聚化的可能性。在此，我们证明，当在同一大肠杆菌细胞中共表达时，PDK家族的两个成员PDK1和PDK2会形成异源二聚体。通过亲和层析将体内产生的异源二聚体激酶纯化至接近均一性。纯化后的激酶很稳定，亚基不会重新组合。异源二聚体激酶具有催化活性，在动力学参数、位点特异性和调节方面明显不同于同源二聚体PDK1或PDK2。这些数据有力地表明，除了基因多样性产生的差异外，PDK1和PDK2之间的异源二聚化给这个蛋白家族增添了另一层次的多样性。
