Goldberger G, Abraham G N, Williams J, Colten H R
J Biol Chem. 1980 Aug 10;255(15):7071-4.
The amino acid sequence of the NH2-terminal regions of the intracellular precursor of the fourth component of guinea pig complement (pro-C4) and isolated alpha, beta, and gamma chains of native C4, synthesized by peritoneal macrophages in culture, were determined with a microradiosequencing technique. Radiolabeled pro-C4 was immunoprecipitated from cell lysates and native C4 from culture media which contained one of six 3H-amino-acids or [35S]methionine. The purity of these proteins was established and molecular weights were estimated by electrophoresis in sodium dodecyl sulfate. Seventeen of the first 22 residues of pro-C4 were identified. Fifteen of these 17 were nonpolar. The eight amino acids ascertained within the first 9 NH2-terminal residues of guinea pig pro-C4 were identical with those reported for human C4 beta chain, and identity with residues determined for guinea pig C4 beta chain was established. These data indicate that beta chain is the NH2-terminal segment of pro-C4, that no residues are cleaved from the NH2 terminus during the conversion to native C4, and that this segment of the pro-C4 molecule is conserved phylogenetically.
采用微量放射测序技术测定了豚鼠补体第四成分（pro-C4）细胞内前体的NH2末端区域以及培养的腹腔巨噬细胞合成的天然C4分离的α、β和γ链的氨基酸序列。从细胞裂解物中免疫沉淀放射性标记的pro-C4，从含有六种3H-氨基酸之一或[35S]甲硫氨酸的培养基中免疫沉淀天然C4。通过十二烷基硫酸钠电泳确定了这些蛋白质的纯度并估计了分子量。确定了pro-C4前22个残基中的17个。这17个残基中的15个是非极性的。在豚鼠pro-C4的前9个NH2末端残基中确定的8个氨基酸与报道的人C4β链的氨基酸相同，并确定了与豚鼠C4β链确定的残基相同。这些数据表明，β链是pro-C4的NH2末端片段，在转化为天然C4的过程中，NH2末端没有残基被切割，并且pro-C4分子的这一片段在系统发育上是保守的。
