鉴定(生物学)
化学
生物化学
基因
磷酸酶
基因产物
分子生物学
生物
酶
基因表达
植物
作者
Jun Zhang,Lifang Zhang,Sumin Zhao,Ernest Y.C. Lee
出处
期刊:Biochemistry
[American Chemical Society]
日期:1998-10-29
卷期号:37 (47): 16728-16734
被引量:57
摘要
The catalytic subunit of mammalian protein phosphatase-1 (PP1) is known to bind to a number of regulatory subunits, whose functions include the targeting of the catalytic subunit to the molecular proximity of its substrate proteins. In addition, PP1 is potently inhibited by several inhibitory polypeptides that include inhibitor-1 and inhibitor-2. In this study the yeast two-hybrid system was used to screen a human cDNA library for putative PP1-binding proteins. Ten putative positive clones were identified, one of which was found to be a partial cDNA of the hemochromatosis candidate gene V (HCG V) whose function was previously unknown. The full-length protein of 126 amino acid residues was expressed in Escherichia coli as a glutathione S-transferase fusion protein and also as a nonfusion protein. The recombinant protein inhibited recombinant and rabbit muscle protein phosphatase-1 with IC50s of ca. 1 nM, but did not inhibit PP2A. The term inhibitor-3 is proposed for this novel inhibitor. It is extremely hydrophilic, is heat stable, and behaves anomalously on SDS-PAGE with an apparent molecular mass of 23 kDa and on gel filtration with a relative molecular weight of 55 000, in contrast to its calculated molecular mass of 14 kDa. These characteristics are shared by the previously described protein phosphatase-1 inhibitor-2 and inhibitor-1 proteins.
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