Shreffler D C, Atkinson J P, Chan A C, Karp D R, Killion C C, Ogata R T, Rosa P A
Philos Trans R Soc Lond B Biol Sci. 1984 Sep 6;306(1129):395-403. doi: 10.1098/rstb.1984.0100.
Recent analyses, at the protein and DNA levels of structure, of the murine complement components C4 and the closely related sex-limited protein, Slp have led to new insights into the H-2/S region-linked C4 and Slp genes and their products. The primary products are 200 000 Da precursors which are cleaved, intracellularly and extracellularly, into the the mature alpha-beta-gamma-subunit molecules of plasma. Precursor order of subunits is beta-alpha-gamma; a complementary DNA clone spanning the alpha-gamma junction has been extensively analysed. The C-terminal of the alpha-chain is of particular interest because of post-secretion processing which differentiates 'secreted' and 'plasma' forms of C4, both apparently functional, and because allelic variants of C4 and the Slp protein, which differ substantially in molecular masses, owe their differences principally to different levels of glycosylation of the alpha-chain. Allelic variations in rate of C4 synthesis (C4-high compared with C4-low) have been analysed in cultures of hepatocytes and macrophages. Three distinct modes of genetic regulation of the expression of the Slp protein have been identified.
最近在蛋白质和DNA结构水平上对小鼠补体成分C4以及密切相关的性别限制蛋白Slp进行的分析，为与H-2/S区域连锁的C4和Slp基因及其产物带来了新的见解。主要产物是200000 Da的前体，它们在细胞内和细胞外被切割成血浆中的成熟α-β-γ亚基分子。亚基的前体顺序是β-α-γ；一个跨越α-γ连接点的互补DNA克隆已被广泛分析。α链的C末端特别受关注，这是因为分泌后加工区分了C4的“分泌型”和“血浆型”，二者显然都有功能，还因为C4和Slp蛋白的等位基因变体在分子量上有很大差异，其差异主要归因于α链糖基化水平的不同。已在肝细胞和巨噬细胞培养物中分析了C4合成速率的等位基因变异（C4高与C4低相比）。已确定了Slp蛋白表达的三种不同遗传调控模式。
