Speicher D W, Morrow J S, Knowles W J, Marchesi V T
J Biol Chem. 1982 Aug 10;257(15):9093-101.
Proteolytic susceptibility has been used to probe the structure of human erythrocyte spectrin. Nine unique polypeptide segments have been defined by mild trypsin digestion (0 degrees C) and analyzed by two-dimensional peptide mapping techniques. These peptide segments, referred to operationally as chemical domains, exhibited varying degrees of sensitivity to further proteolytic cleavage. One region (beta I) which contained the phosphorylated amino acids of the beta subunit was quite sensitive to proteolysis and was rapidly degraded to numerous small peptides. Overlap peptides produced by enzymatic and chemical cleavages were used to align each domain in the appropriate spectrin subunit. The molecular weights of the largest unique peptides from both subunits sum to the approximate weight of the intact molecule. Similarly, summation of the two-dimensional peptide maps of the intermediate sized peptides approximates the two-dimensional maps of the intact spectrin subunits, indicating that most or all of the molecule is represented. These results suggest that spectrin is composed of multiple, ordered, largely alpha-helical domains that are connected by small protease-sensitive segments. A comprehensive structural model is presented.
蛋白水解敏感性已被用于探究人红细胞血影蛋白的结构。通过温和的胰蛋白酶消化（0℃）定义了九个独特的多肽片段，并采用二维肽图技术进行分析。这些肽段在操作上被称为化学结构域，对进一步的蛋白水解切割表现出不同程度的敏感性。包含β亚基磷酸化氨基酸的一个区域（βI）对蛋白水解相当敏感，并迅速降解为许多小肽。通过酶切和化学切割产生的重叠肽用于在适当的血影蛋白亚基中排列每个结构域。来自两个亚基的最大独特肽的分子量之和接近完整分子的近似重量。同样，中等大小肽的二维肽图之和近似于完整血影蛋白亚基的二维图，表明该分子的大部分或全部都有体现。这些结果表明，血影蛋白由多个有序的、主要为α螺旋的结构域组成，这些结构域由小的蛋白酶敏感片段连接。本文提出了一个全面的结构模型。
