Increased concentration of an apparently identical cellular protein in cells transformed by either Abelson murine leukemia virus or other transforming agents
Increased concentration of an apparently identical cellular protein in cells transformed by either Abelson murine leukemia virus or other transforming agents
复制标题
由阿贝尔森鼠白血病病毒或其他转化剂转化的细胞中明显相同的细胞蛋白浓度增加
作者：
V. Rotter;M. Boss;D. Baltimore
Abelson小鼠白血病病毒(A-MuLV)转化的细胞、猿猴病毒40(SV40)转化的细胞和化学转化的细胞都增加了50,000分子量宿主细胞蛋白的水平。用A-MuLV转化细胞和化学转化细胞的血清检测到该蛋白，并在SV40转化细胞的提取液中与T抗原紧密结合。部分酶消化显示，这三种来源的蛋白质都是无法区分的。这三种蛋白质在细胞中被磷酸化，而磷酸与A-MuLV相关的P50的连接是丝氨酸残基。免疫荧光显示，正常淋巴样细胞和A-MuLV转化的淋巴样细胞表面均有P50相关蛋白表达，但细胞分级显示转化细胞的胞浆中大部分P50是游离的。免疫荧光显示，未转化成纤维细胞和SV40转化成纤维细胞胞浆中均有P50表达。其他细胞则呈现模糊的图案。Cocap实验表明，A-MuLV特异的P120蛋白与淋巴细胞表面P50相关蛋白的结合很弱，但免疫沉淀法没有发现P120和P50的结合。尽管在许多研究中使用了抗P50的单抗血清，但大量P50蛋白与细胞表面反应分子的同一性还需要进一步研究。
Abelson murine leukemia virus (A-MuLV)-transformed cells, simian virus 40 (SV40)-transformed cells, and chemically transformed cells all have increased levels of a 50,000-molecular-weight host cell protein. The protein was detected with sera raised to the A-MuLV-transformed and chemically transformed cells and was tightly bound to T-antigen in extracts of SV40-transformed cells. Partial protease digests showed that the proteins from all three sources were indistinguishable. The three proteins were phosphorylated in cells, and the linkage of phosphate to the A-MuLV-associated P50 was to a serine residue. By immunofluorescence methods, P50-related protein was found on the surface of both normal lymphoid cells and A-MuLV-transformed lymphoid cells, but cell fractionation showed that the majority of P50 was free in the cytoplasm of the transformed cells. Immunofluorescence also showed that P50 was found in granules in the cytoplasm of both untransformed and SV40-transformed fibroblasts. Other cells gave indistinct patterns. Cocapping experiments showed that the A-MuLV-specified P120 protein is weakly associated with the surface P50-related protein of lymphoid cells, but no association of P120 and P50 could be demonstrated by immunoprecipitation methods. Although a monoclonal antiserum to P50 was used in many of these studies, the identity of the bulk P50 protein with the molecules that are reactive at the cell surface requires further study.