Hendrix P, Turowski P, Mayer-Jaekel R E, Goris J, Hofsteenge J, Merlevede W, Hemmings B A
Afdeling Biochemie, Faculteit Geneeskunde, Katholieke Universiteit te Leuven, Belgium.
J Biol Chem. 1993 Apr 5;268(10):7330-7.
A dimeric and two trimeric forms of protein phosphatase 2A (PP2A) were purified from rabbit and Xenopus tissues and analyzed using antisera specific for the catalytic and regulatory subunits. The dimeric holoenzyme consists of a complex between a 36-kDa catalytic subunit associated with a approximately 65-kDa regulatory subunit. The two trimeric holoenzymes consist of the catalytic subunit complexed with 65- and 55-kDa subunits, or 65- and 72-kDa subunits. Antisera were raised against synthetic peptides specific for the alpha- and beta-isoforms of the 65-kDa (PR65 alpha/beta) and 55-kDa (PR55 alpha/beta) subunits identified by molecular cloning. Anti-peptide antisera to the 36-kDa catalytic subunit of PP2A were prepared against two selected regions: one specific for the alpha-isoform and one to a peptide common to both the alpha- and beta-isoforms. Immunochemical analysis of all three mammalian holoenzymes showed that the catalytic, 55- and 65-kDa subunits are both predominantly of the alpha-isoform, which is consistent with the peptide sequence data. The 65-kDa subunit of PP2A holoenzymes isolated from Xenopus skeletal muscle reacted with both anti-alpha and anti-beta PR65-specific antisera whereas the PP2A holoenzymes isolated from Xenopus oocytes reacted preferentially with the beta-specific antisera, indicating developmental changes in the expression of the 65-kDa subunit isoform. Taken together, these results show that the "core" subunits of the PP2A holoenzymes consist of the catalytic complexed with the 65-kDa subunit and that the association of the third subunit does not appear to be influenced by the isoform of these two core subunits.
从兔和非洲爪蟾组织中纯化出蛋白磷酸酶2A（PP2A）的二聚体形式和两种三聚体形式，并使用针对催化亚基和调节亚基的抗血清进行分析。二聚体全酶由一个36 kDa催化亚基与一个约65 kDa调节亚基形成的复合物组成。两种三聚体全酶由催化亚基分别与65 kDa和55 kDa亚基，或65 kDa和72 kDa亚基复合而成。针对通过分子克隆鉴定出的65 kDa（PR65α/β）和55 kDa（PR55α/β）亚基的α-和β-同工型的合成肽制备了抗血清。针对PP2A的36 kDa催化亚基的抗肽抗血清是针对两个选定区域制备的：一个对α-同工型特异，另一个对α-和β-同工型共有的肽段特异。对所有三种哺乳动物全酶的免疫化学分析表明，催化亚基、55 kDa和65 kDa亚基主要都是α-同工型，这与肽序列数据一致。从非洲爪蟾骨骼肌分离的PP2A全酶的65 kDa亚基与抗α和抗β PR65特异性抗血清均发生反应，而从非洲爪蟾卵母细胞分离的PP2A全酶则优先与β特异性抗血清发生反应，表明65 kDa亚基同工型的表达存在发育变化。综上所述，这些结果表明，PP2A全酶的“核心”亚基由与65 kDa亚基复合的催化亚基组成，并且第三个亚基的结合似乎不受这两个核心亚基同工型的影响。
