Quill H, Schwartz B D
Mol Immunol. 1983 Dec;20(12):1333-45. doi: 10.1016/0161-5890(83)90164-5.
Analysis of guinea-pig Ia immunoprecipitates by two-dimensional gel electrophoresis demonstrated the specific association of Ia molecules with several types of invariant proteins. These include a 33,000 mol. wt basic protein homologous to murine invariant chain (Ii), and a set of 34,000-36,000 mol. wt proteins more acidic than Ii (acidic invariant chain). Two 23,000-25,000 mol. wt non-polymorphic proteins with pIs of 6.0 and 6.5 were also observed in association with Ia, as was a basic protein of mol. wt 42,000. Pulse/chase studies using [35S]methionine demonstrated that Ii, but not acidic invariant chain, was associated with newly synthesized Ia molecules. The amount of 35S-Ii decreased greatly throughout the chase period. 35S-acidic invariant chain was clearly present in Ia precipitates by 30 min after Ia synthesis, but was not detected 4 hr after synthesis. Only acidic invariant chain was associated with mature Ia antigens bound by the lectin Ricinus communis I. Our results indicate that guinea-pig invariant proteins are differentially bound by Ia molecules during maturation of Ia alpha- and beta-chains, and suggest that acidic invariant chain could be a processed form of Ii.
通过二维凝胶电泳对豚鼠Ia免疫沉淀物进行分析，结果表明Ia分子与几种类型的恒定蛋白存在特异性关联。这些恒定蛋白包括一种分子量为33,000的碱性蛋白，它与小鼠恒定链（Ii）同源，以及一组分子量在34,000 - 36,000之间、比Ii更具酸性的蛋白（酸性恒定链）。还观察到两种分子量为23,000 - 25,000、pI分别为6.0和6.5的非多态性蛋白与Ia相关联，以及一种分子量为42,000的碱性蛋白。使用[35S]甲硫氨酸进行的脉冲/追踪研究表明，与新合成的Ia分子相关联的是Ii，而非酸性恒定链。在整个追踪期间，35S-Ii的量大幅减少。在Ia合成后30分钟时，Ia沉淀物中明显存在35S-酸性恒定链，但在合成后4小时未检测到。只有酸性恒定链与蓖麻凝集素I结合的成熟Ia抗原相关联。我们的结果表明，在Iaα链和β链成熟过程中，豚鼠恒定蛋白与Ia分子的结合存在差异，这表明酸性恒定链可能是Ii的一种加工形式。
