Hemler M E, Huang C, Schwarz L
J Biol Chem. 1987 Mar 5;262(7):3300-9.
The family of human cell surface heterodimers which includes VLA-1 and VLA-2 is now shown to include three additional heterodimers, here called VLA-3, VLA-4, and VLA-5. Each of these separate VLA structures is composed of a distinct alpha subunit (Mr 110,000-200,000 nonreduced) noncovalently associated with a common beta subunit (Mr 110,000 nonreduced). Chemical cross-linking experiments provided evidence that each VLA complex exists predominantly as a 1:1 alpha beta heterodimer. The VLA proteins are widely distributed, with one or more of the heterodimers present on nearly all cell types tested. Evidence for five distinct VLA alpha subunits was obtained from differences observed in antibody recognition, cell distribution patterns, two-dimensional gel analyses, and V8 protease cleavage patterns. On the other hand, the beta subunit present in each heterodimer was immunochemically and electrophoretically indistinguishable, and yielded identical V8 cleavage fragments. Immunoblotting experiments revealed that besides the Mr 110,000 beta normally seen, another beta protein was present that is smaller in size (Mr 90,000 nonreduced), altered or deficient in glycosylation, and not available for cell surface radiolabeling.
包括VLA - 1和VLA - 2在内的人类细胞表面异二聚体家族，现已发现还包括另外三种异二聚体，这里称为VLA - 3、VLA - 4和VLA - 5。这些各自独立的VLA结构均由一个独特的α亚基（非还原状态下Mr为110,000 - 200,000）与一个共同的β亚基（非还原状态下Mr为110,000）非共价结合而成。化学交联实验提供了证据，表明每个VLA复合物主要以1:1的αβ异二聚体形式存在。VLA蛋白广泛分布，在几乎所有测试的细胞类型上都存在一种或多种异二聚体。从抗体识别、细胞分布模式、二维凝胶分析以及V8蛋白酶切割模式中观察到的差异，获得了存在五种不同VLAα亚基的证据。另一方面，每个异二聚体中存在的β亚基在免疫化学和电泳方面无法区分，并且产生相同的V8切割片段。免疫印迹实验显示，除了通常可见的Mr为110,000的β蛋白外，还存在另一种β蛋白，其大小较小（非还原状态下Mr为90,000），糖基化改变或缺乏，并且不能用于细胞表面放射性标记。
