鯉魚及牛蛙水晶蛋白之研究

Abstract

從鯉魚水晶蛋白的分析知道含有高甲硫胺酸（high-methionine）的γ水晶蛋白。由其cDNA庫篩選兩個高甲硫胺酸菌株（high-methionine clone):γ-ml,γ-m2。兩者的cDNA與翻譯的蛋白質序列相類性（homology）皆為75%。 牛蛙蝌蚪在變態時水晶蛋白有顯著的變化。一是α與γ水晶蛋白佔總蛋白質量降低，二是－β水晶蛋白（BC3或β29）由少於百分之一總蛋白質量增至百分之五點五左右。分析此一蛋白質，發現它與牛的β Bp有相當高的相類性（homology）。用相類性比較定序（Sequencing by homology）定出了約75%的蛋白質序列，這75%中與β Bp的相類性為80% 文中並對此二種蛋白質的結構、演化角色與可能功能作一討論。

Carp lens contain unusually high methionine (12-15%) γ-crystallins. We got two γ-crystallins clones of such high-methionine contents from the cDNA library of carp, that is, γ-m1 and γ-m2. The amino acid and nucieotide sequence homology between γ-m1 and γ-m2 are about 75%. The crystallin patterns of bullfrog undergo visible changes during its metamorphosis. One change is the decrease of contents of α-and γ-crysta1lins; the other is the increase of a β-crystallin (BC3 or β29), that is, from less 1% of total protein to 5.5% of total protein. analysing and sequencing by homology, we determined 75% sequence of this protein. In this 75% sequence the protein has 80% homology with βBp of bovine. The stucture, evolution and possible function of these proteins are discussed.