鯉魚 Gamma 水晶蛋白基因的研究

Abstract

中文摘要 鯉魚的γ水晶蛋白基因富含有 ATG序列 ，且其蛋白質亦含有多量的甲硫胺酸。利用鯉魚水晶蛋白的γ－ml cDNA 作探針篩選含有鯉魚水晶蛋白的基因庫，得到兩個的 clone ，編號為 B163 , B32O 然後利用 RsaI / TaqI 酵素，在 pUC19 上做同向序列定序。得到一個與已知 γ－ml exon 基因序列近乎 99 ％相似的基因。但其 intron 卻有很大變異。這個現象可能在基因演化與調控機制上有特殊意義。另外還得到兩個富含 ATG 序列的水晶蛋白部分基因。由這些結果加上已知的 γ－ml , γ－m2 , γ－m3 基因估計鯉魚的 γ 水晶蛋白基因族（ Gene family ) ，至水含有五種類似的 γ 水晶蛋白基因。

Gamma-crystallins are the major water-soluble proteins in vertebrate eye lens and the more interesting thing is that they are encoded by a closely related gene family. We have investigated the complexity of the carp γ-crystallin gene family by Southern hybridization, and have secreened at least 2 different clones, B32 and B163 containting γ-crystallin within the carp genomic library. Aoso the DNA fragment of interest cloned in pUC19 was further analyzed by “unidirection endonuclease deletion method”. After characterization, on of the positive clones, which contains a 4.2Kb-fragment from B163, was shown to carry a full-size γ-crystallin gene. Especially, more intriguing is finding that the homology of all the exon sequences between γ-m4 (from 4.2Kb fragment) and γ-ml is highly 99%, but their introns are quite different. The other clones, was found to contain many in-frame ATG codons and also belongs to γ-crystallin genes. According to the present result, the carp γ-crystallin gene family is composed of at least 5 genes, including the previously reported γ-ml γ-m2 and γ -m3.