Goffenberg S I, Panchenko M P, Zhuravlev I V, Tkachuk V A
Biokhimiia. 1990 May;55(5):878-87.
A 23 kDa GTP-binding protein was purified from pig heart sarcolemma. This protein was not ADP-ribosylated by cholera, pertussis and botulinum C3 toxins. In pig heart sarcolemma pertussis toxin ADP-ribosylated 40 kDa subunit of Gi-protein, cholera toxin--45 kDa subunit of Gs-protein, botulinum C3 toxin ADP-ribosylated a group of proteins with Mr 22, 26 and 29 kDa. Antiserum generated against the peptide common for all alpha-subunits of G-proteins did not react with purified 23 kDa protein. Trypsin cleaved the 23 kDa protein in the presence of guanyl nucleotides into a 22 kDa fragment. Proteolysis of the 39 kDa alpha 0-subunit from bovine brain plasma membranes and ADP-ribosylated 40 kDa alpha i-subunit from pig heart sarcolemma in the presence of GTP gamma S yielded the 37 and 38 kDa fragments, respectively. In the presence of GTP and GDP the proteolysis of alpha 0 yielded the 24 and 15 kDa fragments, while the proteolysis of ADP-ribosylated alpha i-subunit yielded a labelled 16 kDa peptide. Irrespective of nucleotides trypsin cleaved the ADP-ribosylated 26 kDa substrate of botulinum C3 toxin into two labelled peptides with Mr 24 and 17 kDa. The data obtained indicate the existence in pig heart sarcolemma of a new 23 kDa GTP-binding protein with partial homology to the alpha-subunits of "classical" G-proteins.
从猪心脏肌膜中纯化出一种23 kDa的GTP结合蛋白。该蛋白不会被霍乱毒素、百日咳毒素和肉毒杆菌C3毒素进行ADP核糖基化修饰。在猪心脏肌膜中，百日咳毒素可使Gi蛋白的40 kDa亚基发生ADP核糖基化，霍乱毒素可使Gs蛋白的45 kDa亚基发生ADP核糖基化，肉毒杆菌C3毒素可使一组分子量为22、26和29 kDa的蛋白发生ADP核糖基化。针对G蛋白所有α亚基共有的肽段产生的抗血清，不会与纯化的23 kDa蛋白发生反应。在鸟苷核苷酸存在的情况下，胰蛋白酶将23 kDa蛋白切割成一个22 kDa的片段。在GTPγS存在的情况下，对牛脑质膜中的39 kDaα0亚基和猪心脏肌膜中经ADP核糖基化修饰的40 kDaαi亚基进行蛋白水解，分别产生37 kDa和38 kDa的片段。在GTP和GDP存在的情况下，α0亚基的蛋白水解产生24 kDa和15 kDa的片段，而经ADP核糖基化修饰的αi亚基的蛋白水解产生一个标记的16 kDa肽段。无论核苷酸存在与否，胰蛋白酶都会将肉毒杆菌C3毒素的ADP核糖基化修饰的26 kDa底物切割成两个标记的肽段，分子量分别为24 kDa和17 kDa。所获得的数据表明，猪心脏肌膜中存在一种新的23 kDa GTP结合蛋白，它与“经典”G蛋白的α亚基具有部分同源性。
