Crowe A J, Hayman M J
Department of Microbiology, State University of New York, Stony Brook 11794.
Oncogene. 1993 Jan;8(1):181-9.
The transforming gene product of the S13 avian erythroblastosis virus, env-sea, is a member of the growth factor receptor class of tyrosine kinases. The env-sea precursor protein gp155env-sea is proteolytically processed into the mature cleavage products gp85env-sea and gp70env-sea which are subsequently terminally glycosylated. Previous studies have shown that the abnormal glycosylation of gp155env-sea which takes place in the presence of the inhibitor castanospermine inhibits the proteolytic cleavage of gp155env-sea and blocks its transforming ability. To define a role for proteolytic processing of env-sea in transformation, we have introduced mutations at the protease recognition site which efficiently block cleavage without affecting the biosynthesis or transport of the resulting uncleaved protein. We show here that an uncleaved but fully glycosylated sea-encoded protein retains the ability to transform chicken embryo fibroblasts, indicating that proteolytic processing is not essential for transformation by the env-sea tyrosine kinase.
S13禽成红细胞增多症病毒的转化基因产物env-sea是酪氨酸激酶生长因子受体家族的一员。env-sea前体蛋白gp155env-sea经蛋白水解加工成成熟的裂解产物gp85env-sea和gp70env-sea，随后进行终末糖基化。先前的研究表明，在抑制剂栗精胺存在的情况下，gp155env-sea发生的异常糖基化会抑制gp155env-sea的蛋白水解裂解，并阻断其转化能力。为了确定env-sea的蛋白水解加工在转化中的作用，我们在蛋白酶识别位点引入了突变，这些突变有效地阻断了裂解，而不影响所得未裂解蛋白的生物合成或运输。我们在此表明，未裂解但完全糖基化的sea编码蛋白保留了转化鸡胚成纤维细胞的能力，这表明蛋白水解加工对于env-sea酪氨酸激酶的转化并非必不可少。
