Frénoy J P, Bourrillon R
Biochimie. 1977;59(4):351-4. doi: 10.1016/s0300-9084(77)80310-6.
SDS-polyacrylamide gel electrophoresis of a recently prepared alpha 2-macroglobulin solution showed only the polypeptide chains of 190,000 molecular weight. Reduction-alkylation of this preparation followed by gel-filtration on a Sephadex G-200 column in 5.2 M guanidine hydrochloride was unable to separate a fraction of 83,000 molecular weight as previously described. Nevertheless, after incubation of a mixture alpha 2-macroglobulin-trypsin during 45 minutes at 37 degrees C, approximately 60 per cent of the preparation were converted in a component with 83,000 molecular weight as detected in SDS polyacrylamide gel. That component was isolated on Sephadex G-200 in guanidine hydrochloride and corresponds to the subunit, fraction II. According to the results of the present work together with those of previous studies, it can be assumed that alpha 2-MG is a 780,000 molecular weight protein (19S) formed of two half-molecules of equal weight (11-12S). The half-molecule contains two polypeptide chains of 180,000-190,000 molecular weight, each of them having, in its middle, a specific region particularly susceptible to attack by proteases.
最近制备的α2-巨球蛋白溶液的SDS-聚丙烯酰胺凝胶电泳仅显示出分子量为190,000的多肽链。该制剂经还原烷基化处理后，在含5.2M盐酸胍的葡聚糖凝胶G-200柱上进行凝胶过滤，无法如先前所述分离出分子量为83,000的组分。然而，在37℃下将α2-巨球蛋白-胰蛋白酶混合物孵育45分钟后，约60%的制剂转化为在SDS聚丙烯酰胺凝胶中检测到的分子量为83,000的组分。该组分在含盐酸胍的葡聚糖凝胶G-200上分离得到，对应于亚基，即组分II。根据本研究结果以及先前的研究结果，可以假设α2-MG是一种分子量为780,000的蛋白质（19S），由两个等重的半分子（11-12S）组成。半分子包含两条分子量为180,000-190,000的多肽链，每条多肽链在中间都有一个特别容易受到蛋白酶攻击的特定区域。
