Schoenmakers J G, den Dunnen J T, Moormann R J, Jongbloed R, van Leen R W, Lubsen N H
Ciba Found Symp. 1984;106:208-18. doi: 10.1002/9780470720875.ch12.
Recent work from our laboratory on the structure and the genetic organization of the lens beta- and gamma-crystallin gene families is reviewed briefly. In the rat six different gamma-crystallin genes are present which all have an identical distribution of exons and introns, namely a small intron after the third translation codon and a larger one within the coding region for the connecting peptide which links the two domains of the gamma-crystallins. We find five rat genes physically linked and located on a DNA segment of only 50 kilobases, whereas the sixth gene is more distant. The polypeptide sequences, as deduced from DNA sequence analysis, of these six rat and two human gamma-crystallin genes are compared and discussed in terms of structural and evolutionary aspects. The gene coding for rat beta B1a-crystallin appears to be a single-copy gene of much larger size than the gamma-crystallin genes. The beta B1 gene is not physically linked to the other beta-crystallin genes, even though the various beta genes are evolutionarily related and in that sense constitute a gene family. In contrast to the gamma-crystallin genes, the beta B1 gene has an intron not only between the domain sequence but also between the motif sequences. In addition, the exon coding for the N-terminal extension of the protein is separated by an intron from the first protein motif sequence. We anticipate that structural and genetic investigations on lens crystallin genes and their expression might provide a framework for revealing the basis of (some) hereditary disorders in the visual system.
本文简要回顾了我们实验室近期关于晶状体β-和γ-晶状体蛋白基因家族的结构和遗传组织的研究工作。在大鼠中存在六个不同的γ-晶状体蛋白基因，它们的外显子和内含子分布完全相同，即在第三个翻译密码子之后有一个小内含子，在连接γ-晶状体蛋白两个结构域的连接肽的编码区域内有一个较大的内含子。我们发现五个大鼠基因在物理上是连锁的，位于仅50千碱基的DNA片段上，而第六个基因则距离较远。从DNA序列分析推导得出的这六个大鼠和两个人类γ-晶状体蛋白基因的多肽序列，从结构和进化方面进行了比较和讨论。编码大鼠βB1a-晶状体蛋白的基因似乎是一个单拷贝基因，其大小比γ-晶状体蛋白基因大得多。βB1基因在物理上不与其他β-晶状体蛋白基因连锁，尽管各种β基因在进化上相关，从这个意义上说构成一个基因家族。与γ-晶状体蛋白基因不同，βB1基因不仅在结构域序列之间有一个内含子，而且在基序序列之间也有一个内含子。此外，编码蛋白质N端延伸的外显子与第一个蛋白质基序序列被一个内含子隔开。我们预计，对晶状体晶状体蛋白基因及其表达的结构和遗传研究可能为揭示视觉系统中（某些）遗传性疾病的基础提供一个框架。
