Anderson S J, Naso R B
Cell. 1980 Oct;21(3):837-47. doi: 10.1016/0092-8674(80)90447-x.
A glycoprotein of molecular weight 130,000 (gP130) has been precipitated from the cytoplasm of GR-strain mouse mammary tumor (GR-MMT) cells by a rabbit antiserum (anti-MMTV) to GR-strain mouse mammary tumor virus (GR-MMTV). This protein was not precipitated by antisera specific for detergent-disrupted C3H-strain MMTV (C3H-MMTV); C3H-MMTV glycoproteins; C3H-MMTV nonglycosylated proteins; GR-MMTV p25 or p12; RIII strain (milk) MMTV proteins; or Rauscher murine leukemia virus (R-MuLV) proteins; nor was it precipitated by normal rabbit serum. Two-dimensional thin layer analysis of 35S-methionine-containing tryptic peptides revealed that five of nine gp33 peptides and one of seven gp55 peptides are shared by gP130 and gPr76env. The envelope protein precursor, gPr76env, contains all of the gp33 peptides and six of seven gp55 peptides. One peptide in gPr76env, possibly a gp55-gp33 junction peptide, is also apparently present in gP130. Six of ten p25 peptides and four more gag-related peptides are shared by PR78gag and gP130. Protein gP130 also contains several tryptic peptides not found in gPr76env or in the core protein precursors Pr78gag, Pr110gag or Pr180gag-pol. Radioimmunoprecipitation experiments showed that gP130 could be precipitated from extracts of GR-MMTV cells with anti-MMTV serum even after antibodies to the known MMTV structural proteins had been removed from the serum by absorption. Both gP130 and a second protein, p30, were found in immunoprecipitates of detergent-disrupted isotopically labeled GR-MMTV treated with the absorbed anti-MMTV serum. These results suggest that antibodies to gP130 in the anti-MMTV serum are capable of recognizing those protein sequences unique to gP130; that is, those protein sequences which are not related to viral structural proteins. In light of these data and data published previously, gP130 is apparently a polyprotein containing juxtaposed components translated from the 5' and 3' end of the MMTV genome and protein components not previously identified as virus-specific.
用兔抗GR株小鼠乳腺肿瘤病毒（GR-MMTV）血清（抗MMTV）从GR株小鼠乳腺肿瘤（GR-MMT）细胞的细胞质中沉淀出一种分子量为130,000的糖蛋白（gP130）。抗去污剂处理的C3H株MMTV（C3H-MMTV）、C3H-MMTV糖蛋白、C3H-MMTV非糖基化蛋白、GR-MMTV p25或p12、RIII株（乳汁）MMTV蛋白或劳氏肉瘤病毒（R-MuLV）蛋白的特异性抗血清均不能沉淀该蛋白；正常兔血清也不能沉淀该蛋白。对含35S-甲硫氨酸的胰蛋白酶肽段进行二维薄层分析表明，gP130与gPr76env共有9个gp33肽段中的5个和7个gp55肽段中的1个。包膜蛋白前体gPr76env包含所有的gp33肽段和7个gp55肽段中的6个。gPr76env中的一个肽段，可能是一个gp55-gp33连接肽段，在gP130中也明显存在。PR78gag和gP130共有10个p25肽段中的6个和另外4个与gag相关的肽段。蛋白gP130还包含一些在gPr76env或核心蛋白前体Pr78gag、Pr110gag或Pr180gag-pol中未发现的胰蛋白酶肽段。放射免疫沉淀实验表明，即使通过吸收从血清中去除了针对已知MMTV结构蛋白的抗体，gP130仍可被抗MMTV血清从GR-MMTV细胞提取物中沉淀出来。在用吸收后的抗MMTV血清处理去污剂破坏的同位素标记的GR-MMTV的免疫沉淀物中发现了gP130和第二种蛋白p30。这些结果表明，抗MMTV血清中针对gP130的抗体能够识别gP130特有的那些蛋白序列；也就是说，那些与病毒结构蛋白无关的蛋白序列。根据这些数据和先前发表的数据，gP130显然是一种多蛋白，包含从MMTV基因组5'端和3'端翻译而来的并列成分以及以前未被鉴定为病毒特异性的蛋白成分。
