Fisher W K, Thompson E O
Aust J Biol Sci. 1976 Mar;29(1-2):57-72.
Myoglobin isolated from skeletal muscle of the platypus contains 153 amino acid residues. The complete amino acid sequence has been determined following cleavage with cyanogen bromide and further digestion of the four fragments with trypsin, chymotrypsin, pepsin and thermolysin. Sequences of the purified peptides were determined by the dansyl-Edman procedure. The amino acid sequence showed 25 differences from human myoglobin and 24 from kangaroo myoglobin. Amino acid sequences in myoglobins are more conserved than sequences in the alpha- and beta-globin chains, and platypus myoglobin shows a similar number of variations in sequence to kangaroo myoglobin when compared with myoglobin of other species. The date of divergence of the platypus from other mammals was estimated at 102 +/- 31 million years, based on the number of amino acid differences between species and allowing for mutations during the evolutionary period. This estimate differs widely from the estimate given by similar treatment of the alpha- and beta-chain sequences and a constant rate of mutation of globin chains is not supported.
从鸭嘴兽骨骼肌中分离出的肌红蛋白含有153个氨基酸残基。在用溴化氰裂解并进一步用胰蛋白酶、糜蛋白酶、胃蛋白酶和嗜热菌蛋白酶消化这四个片段后，已确定了完整的氨基酸序列。通过丹磺酰-埃德曼法测定了纯化肽段的序列。该氨基酸序列与人类肌红蛋白有25个差异，与袋鼠肌红蛋白有24个差异。肌红蛋白中的氨基酸序列比α-和β-珠蛋白链中的序列更保守，与其他物种的肌红蛋白相比，鸭嘴兽肌红蛋白在序列上的变异数量与袋鼠肌红蛋白相似。根据物种间氨基酸差异的数量并考虑进化期间的突变情况，估计鸭嘴兽与其他哺乳动物的分化时间为1.02±0.31亿年前。这一估计与对α-和β-链序列进行类似处理得出的估计有很大差异，且不支持珠蛋白链的恒定突变率。
