Benson M D, DiBartola S P, Dwulet F E
Rheumatology Section, Richard L. Roudebush Veterans Administration Medical Center, Indianapolis, IN 46202.
J Lab Clin Med. 1989 Jan;113(1):67-72.
Amyloid fibrils were isolated from kidney tissue of a cow afflicted with renal failure caused by spontaneous reactive amyloidosis. These fibrils were reduced and alkylated, and the amyloid subunit protein was isolated on a column of Sepharose CL6B. The protein was fragmented with both trypsin and Staphylococcus protease, and the resultant peptides were separated by high-performance liquid chromatography. Sequence analysis gave the complete primary structure of the protein with overlaps of the tryptic peptides confirmed by the Staphylococcus protease peptides. Comparison of the bovine amyloid A (AA) amino acid sequence with human protein AA demonstrates complete invariability from human position 33 to 45 and a very high degree of homology from positions 16 to 29 and 46 to 63. These data indicate that these portions of the molecule may be significant factors in amyloid fibrilogenesis. The bovine AA protein shows a blocked amino terminus, as is the case with the dog and the cat AA proteins. In addition, this protein contains an insertion of nine amino acid residues between human positions 69 and 70. The existence of an additional six residues after position 76 makes the bovine AA an unusually large 90 amino acid peptide. These findings point to a high tolerance for mutation in the carboxyl end of the molecule.
淀粉样纤维是从一头因自发性反应性淀粉样变性导致肾衰竭的奶牛的肾脏组织中分离出来的。这些纤维经过还原和烷基化处理，然后在琼脂糖CL6B柱上分离出淀粉样亚基蛋白。该蛋白用胰蛋白酶和葡萄球菌蛋白酶进行酶解，所得肽段通过高效液相色谱法分离。序列分析给出了该蛋白完整的一级结构，胰蛋白酶肽段的重叠部分由葡萄球菌蛋白酶肽段证实。牛淀粉样蛋白A（AA）氨基酸序列与人类蛋白AA的比较表明，从人类序列的第33位到45位完全相同，从第16位到29位以及第46位到63位具有高度同源性。这些数据表明，分子的这些部分可能是淀粉样纤维形成的重要因素。牛AA蛋白的氨基末端是封闭的，狗和猫的AA蛋白也是如此。此外，该蛋白在人类序列的第69位和70位之间插入了九个氨基酸残基。在第76位之后还存在另外六个残基，使得牛AA成为一个异常大的90个氨基酸的肽段。这些发现表明该分子羧基末端对突变具有高度耐受性。
