人补体成分C4。关于用C3b灭活剂裂解C4b产生的片段的结构研究。

Human complement component C4. Structural studies on the fragments derived from C4b by cleavage with C3b inactivator.

作者信息

Press E M, Gagnon J

出版信息

Biochem J. 1981 Nov 1;199(2):351-7. doi: 10.1042/bj1990351.

DOI:10.1042/bj1990351

PMID:6978710

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1163378/

Abstract

One of the activation products of C4, C4b, was prepared, and the reactive thiol group on the alpha'-chain was radioactively labelled with iodo[2-14C]acetic acid. The alpha'-chain was isolated and the N-terminal amino acid sequence of the first 13 residues was determined. 2. C4b was cleaved by C3bINA in the presence of C4b-binding protein and C4d and C4c isolated. The radioactive label and therefore the reactive thiol group were located to C4d. 3. C4c was reduced and alkylated and the two alpha'-chain fragments of C4c were separated. 3. The molecular weights, amino acid analyses and carbohydrate content of the three alpha'-chain fragments were determined. C4d has a mol.wt. of 44500 and a carbohydrate content of 6%. The two alpha'-chain fragments of C4c have mol.wts. of 25000 (alpha 3) and 12000 (alpha 4) and carbohydrate contents of 10 and 22% respectively. 4. The N-terminal amino acid sequences of C4d, the alpha 3 and the alpha 4 fragments were determined for 18, 24 and 11 residues respectively and, by comparison with the N-terminal sequence of the C4b alpha'-chain, the 25000-mol.wt. fragment (alpha 3) was shown to be derived from the N-terminal part of the alpha'-chain. 5. C-Terminal analyses were done on the alpha'-chain and its three fragments. Arginine was found to be the C-terminal residue of C4d and of the alpha 3 fragment. The C-terminal residue of the alpha'-chain and of the alpha 4 fragment could not be identified. The order of the three fragments of the alpha'-chain is therefore: alpha 3(25000)--C4d(44500)--alpha 4(12000). The specificity of C3bINA is for an Arg--Xaa peptide bond.

摘要

制备了补体4（C4）的一种激活产物C4b，其α'-链上的反应性巯基用碘[2-¹⁴C]乙酸进行放射性标记。分离出α'-链并测定了前13个残基的N端氨基酸序列。2. 在C4b结合蛋白存在的情况下，C4b被C3bINA裂解，分离出C4d和C4c。放射性标记以及因此反应性巯基定位于C4d。3. C4c被还原并烷基化，C4c的两个α'-链片段被分离。3. 测定了三个α'-链片段的分子量、氨基酸分析结果和碳水化合物含量。C4d的分子量为44500，碳水化合物含量为6%。C4c的两个α'-链片段的分子量分别为25000（α3）和12000（α4），碳水化合物含量分别为10%和22%。4. 分别测定了C4d、α3和α4片段18、24和11个残基的N端氨基酸序列，通过与C4bα'-链的N端序列比较，显示25000分子量的片段（α3）源自α'-链的N端部分。5. 对α'-链及其三个片段进行了C端分析。发现精氨酸是C4d和α3片段的C端残基。无法鉴定α'-链和α4片段的C端残基。因此，α'-链的三个片段的顺序为：α3（25000）--C4d（44500）--α4（12000）。C3bINA的特异性作用于精氨酸-Xaa肽键。