Identification of binding sites on the regulatory A subunit of protein phosphatase 2A for the catalytic C subunit and for tumor antigens of simian virus 40 and polyomavirus
Identification of binding sites on the regulatory A subunit of protein phosphatase 2A for the catalytic C subunit and for tumor antigens of simian virus 40 and polyomavirus
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DOI：
10.1128/mcb.12.11.4872-4882.1992
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发表时间：
1992-11
影响因子：
5.3
通讯作者：
R. Ruediger;D. Roeckel;J. Fait;Anders Bergqvist;G. Magnusson;G. Walter
中科院分区：
文献类型：
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作者：
R. Ruediger;D. Roeckel;J. Fait;Anders Bergqvist;G. Magnusson;G. Walter
蛋白磷酸酶2A由三个亚基组成：催化亚基C和两个调节亚基A和B。A亚基由15个不相同的重复序列组成，具有杆状形状。它与B和C亚单位以及猿猴病毒40小T、多瘤病毒小T和多瘤病毒中T肿瘤抗原相关。我们通过A亚基的定点突变，确定了C亚基和肿瘤抗原在A亚基上的结合位点。二十四个N-和C-末端截短和内部缺失的A进行了测定，通过免疫共沉淀的能力，结合C和肿瘤抗原。发现C结合A的C末端的重复序列11至15，而T抗原结合N末端的重叠但不同的区域。猿猴病毒40小T结合重复序列3至6，多瘤病毒小T和中T结合重复序列2至8。这些数据表明C和T抗原在与A.这对于中等T抗原是最明显的，其只能结合那些为C亚基提供整个结合区域的A亚基分子。我们从我们的结果推断，B也结合到N-末端重复。提出了一个小T/中T/B-A-C复合物的模型。
Protein phosphatase 2A is composed of three subunits: the catalytic subunit C and two regulatory subunits, A and B. The A subunit consists of 15 nonidentical repeats and has a rodlike shape. It is associated with the B and C subunits as well as with the simian virus 40 small T, polyomavirus small T, and polyomavirus medium T tumor antigens. We determined the binding sites on subunit A for subunit C and tumor antigens by site-directed mutagenesis of A. Twenty-four N- and C-terminal truncations and internal deletions of A were assayed by coimmunoprecipitation for their ability to bind C and tumor antigens. It was found that C binds to repeats 11 to 15 at the C terminus of A, whereas T antigens bind to overlapping but distinct regions of the N terminus. Simian virus 40 small T binds to repeats 3 to 6, and polyomavirus small T and medium T bind to repeats 2 to 8. The data suggest cooperativity between C and T antigens in binding to A. This is most apparent for medium T antigen, which can only bind to those A subunit molecules that provide the entire binding region for the C subunit. We infer from our results that B also binds to N-terminal repeats. A model of the small T/medium T/B-A-C complexes is presented.