Garriga J, Segura E, Mayol X, Grubmeyer C, Graña X
Fels Institute for Cancer Research, Temple University School of Medicine, Philadelphia, PA 19140, USA.
Biochem J. 1996 Dec 15;320 ( Pt 3)(Pt 3):983-9. doi: 10.1042/bj3200983.
PITALRE is a human protein kinase belonging to the cell division cycle 2 (CDC2) kinase family, and is the catalytic subunit of a multimeric complex that contains several cellular proteins. PITALRE complexes from several cell lines and tissues phosphorylate retinoblastoma protein and myelin basic protein (MBP). In the present work, we have found that MBP is phosphorylated by PITALRE complexes on both Ser and Thr residues. Two different antibodies raised to PITALRE purified virtually identical kinase activities, as analysed by MBP phosphopeptide mapping and phosphoamino acid analysis. We have identified the proline-directed residue Ser-162 of MBP as a major phosphorylation site for PITALRE. In addition, our results suggest that one of the two MBP proline-directed threonine residues, Thr-97, is also selectively phosphorylated by PITALRE. These data, together with analysis of different peptide substrates derived from sites on MBP that are phosphorylated by PITALRE, indicate that PITALRE is a Ser/Thr proline-directed kinase. In addition, our results show that PITALRE has a substrate site specificity distinguishable from those of the CDC2 and cyclin-dependent kinase 2 (CDK2).
PITALRE是一种属于细胞分裂周期2（CDC2）激酶家族的人类蛋白激酶，是一种包含多种细胞蛋白的多聚体复合物的催化亚基。来自几种细胞系和组织的PITALRE复合物可使视网膜母细胞瘤蛋白和髓鞘碱性蛋白（MBP）磷酸化。在本研究中，我们发现MBP在丝氨酸和苏氨酸残基上均被PITALRE复合物磷酸化。通过MBP磷酸肽图谱分析和磷酸氨基酸分析，针对PITALRE产生的两种不同抗体纯化出了几乎相同的激酶活性。我们已确定MBP的脯氨酸定向残基Ser-162是PITALRE的主要磷酸化位点。此外，我们的结果表明，MBP的两个脯氨酸定向苏氨酸残基之一，Thr-97，也被PITALRE选择性磷酸化。这些数据，连同对源自MBP上被PITALRE磷酸化位点的不同肽底物的分析，表明PITALRE是一种丝氨酸/苏氨酸脯氨酸定向激酶。此外，我们的结果表明，PITALRE具有与CDC2和细胞周期蛋白依赖性激酶2（CDK2）不同的底物位点特异性。
