Hastie C J, Carnegie G K, Morrice N, Cohen P T
Medical Research Council Protein Phosphorylation Unit, Department of Biochemistry, University of Dundee, Dundee DD1 5EH, Scotland, U.K.
Biochem J. 2000 May 1;347 Pt 3(Pt 3):845-55.
Protein phosphatase 4 (PPP4) is a protein serine/threonine phosphatase that has been implicated in microtubule organization at centrosomes. Complexes of PPP4 with high apparent molecular masses (450 and 600 kDa) were purified from mammalian skeletal muscle and testis to near homogeneity. Amino acid sequences derived from a protein component present in both complexes were utilized to identify a human cDNA. The encoded putative PPP4 regulatory subunit (termed PPP4R2), comprising 453 amino acids, had a molecular mass of 50.4 kDa. The interaction of PPP4R2 with PPP4 catalytic subunit (PPP4c) was confirmed by co-sedimentation of PPP4c with PPP4R2 expressed in bacteria and human cells. PPP4c formed a complex of 450 kDa with baculovirus expressed His(6)-tagged PPP4R2. Immunocytological detection of PPP4R2 at centrosomes suggests that it may target PPP4c to this location. Native 450 kDa and 600 kDa PPP4 complexes are inactive, but can be activated by basic proteins, suggesting that PPP4R2 may also regulate the activity of PPP4c at centrosomal microtubule organising centres.
蛋白磷酸酶4（PPP4）是一种蛋白丝氨酸/苏氨酸磷酸酶，与中心体处的微管组织有关。从哺乳动物骨骼肌和睾丸中纯化出具有高表观分子量（450和600 kDa）的PPP4复合物，纯度接近均一。利用从两种复合物中存在的一种蛋白质成分获得的氨基酸序列来鉴定人类cDNA。编码的假定PPP4调节亚基（称为PPP4R2）由453个氨基酸组成，分子量为50.4 kDa。通过PPP4c与在细菌和人类细胞中表达的PPP4R2的共沉降，证实了PPP4R2与PPP4催化亚基（PPP4c）的相互作用。PPP4c与杆状病毒表达的His(6)标记的PPP4R2形成了一个450 kDa的复合物。对中心体处PPP4R2的免疫细胞化学检测表明，它可能将PPP4c靶向该位置。天然的450 kDa和600 kDa PPP4复合物无活性，但可被碱性蛋白激活，这表明PPP4R2也可能在中心体微管组织中心调节PPP4c的活性。
