Keryer G, Luo Z, Cavadore J C, Erlichman J, Bornens M
Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, Gif sur Yvette, France.
Proc Natl Acad Sci U S A. 1993 Jun 15;90(12):5418-22. doi: 10.1073/pnas.90.12.5418.
Subcellular localization of type II cAMP-dependent protein kinase is determined by the interactions of the regulatory subunit (RII) with specific RII-anchoring proteins. By using truncated NH2-terminal RII beta fusion proteins expressed in Escherichia coli and the mitotic protein kinase p34cdc2 isolated from HeLa cells or starfish oocytes, we investigated the in vitro phosphorylation of RII beta by these kinases. The putative site for phosphorylation by the mitotic kinases is Thr-69 in the NH2-terminal domain of RII beta. This phosphorylation site matches the consensus sequence X(T/S)PX(K/R) for p34cdc2 recognition and belongs to a well-conserved sequence found in all RII beta sequences known to date. In contrast to phosphorylation by casein kinase II or the cAMP-dependent protein kinase catalytic subunit, phosphorylation of RII beta by mitotic kinases impaired its interaction with a well-known RII-anchoring protein, the neuronal microtubule-associated protein 2. The potential regulatory significance of the phosphorylation of this site on the interaction with microtubule-associated protein 2 and other RII-anchoring proteins and the physiological relevance of this cyclin B/p34cdc2 kinase-catalyzed modification of RII beta (or phosphorylation by other proline-directed protein kinases) are discussed.
II型环磷酸腺苷依赖性蛋白激酶的亚细胞定位是由调节亚基（RII）与特定RII锚定蛋白的相互作用所决定的。通过使用在大肠杆菌中表达的截短的NH2末端RIIβ融合蛋白以及从HeLa细胞或海星卵母细胞中分离出的有丝分裂蛋白激酶p34cdc2，我们研究了这些激酶对RIIβ的体外磷酸化作用。有丝分裂激酶磷酸化的假定位点是RIIβ的NH2末端结构域中的苏氨酸-69。该磷酸化位点与p34cdc2识别的共有序列X(T/S)PX(K/R)相匹配，并且属于在迄今为止已知的所有RIIβ序列中都存在的一个高度保守的序列。与酪蛋白激酶II或环磷酸腺苷依赖性蛋白激酶催化亚基的磷酸化作用不同，有丝分裂激酶对RIIβ的磷酸化作用损害了它与一种著名的RII锚定蛋白——神经元微管相关蛋白2的相互作用。本文讨论了该位点磷酸化在与微管相关蛋白2及其他RII锚定蛋白相互作用方面的潜在调节意义，以及这种细胞周期蛋白B/p34cdc2激酶催化的RIIβ修饰（或其他脯氨酸定向蛋白激酶的磷酸化作用）的生理相关性。
