Subramanian S V, Wyroba E, Andersen A P, Satir B H
Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461.
Proc Natl Acad Sci U S A. 1994 Oct 11;91(21):9832-6. doi: 10.1073/pnas.91.21.9832.
A cDNA for parafusin, an evolutionarily conserved phosphoglycoprotein involved in exocytosis, has been cloned and sequenced from a unicellular eukaryote, Paramecium tetraurelia. A Paramecium cDNA library was screened with an oligonucleotide probe synthesized to an internal amino acid sequence of isolated parafusin. The insert was 3 kb long with an open reading frame of 1.75 kb. Data base searches of the deduced amino acid sequence showed that Paramecium parafusin had a 50.7% sequence identity to rabbit muscle phosphoglucomutase, although no detectable phosphoglucomutase activity has been detected in isolated parafusin. The deduced parafusin amino acid sequence had four inserts and two deletions, which might confer on the protein specific functions in signal transduction events related to exocytosis. Furthermore, searches for potential phosphorylation sites showed the presence of a protein kinase C site (KDFSFR) specific to parafusin. Southern blot analysis with probes specific for parafusin and phosphoglucomutase suggested that these proteins were products of different genes. We propose that parafusin and phosphoglucomutase are members of a superfamily that conserve homologies important for the tertiary structure of the molecules.
已经从单细胞真核生物四膜虫中克隆并测序了一种与胞吐作用有关的进化保守的磷酸糖蛋白——副融合蛋白的cDNA。用根据分离出的副融合蛋白内部氨基酸序列合成的寡核苷酸探针筛选四膜虫cDNA文库。插入片段长3 kb，有一个1.75 kb的开放阅读框。对推导的氨基酸序列进行数据库搜索表明，四膜虫副融合蛋白与兔肌肉磷酸葡萄糖变位酶的序列同一性为50.7%，尽管在分离出的副融合蛋白中未检测到可检测的磷酸葡萄糖变位酶活性。推导的副融合蛋白氨基酸序列有四个插入和两个缺失，这可能赋予该蛋白在与胞吐作用相关的信号转导事件中的特定功能。此外，对潜在磷酸化位点的搜索显示存在副融合蛋白特有的蛋白激酶C位点（KDFSFR）。用副融合蛋白和磷酸葡萄糖变位酶特异性探针进行的Southern印迹分析表明，这些蛋白是不同基因的产物。我们提出副融合蛋白和磷酸葡萄糖变位酶是一个超家族的成员，该超家族保留了对分子三级结构很重要的同源性。
