de Jong W W, Leunissen J A, Leenen P J, Zweers A, Versteeg M
Department of Biochemistry, University of Nijmegen, The Netherlands.
J Biol Chem. 1988 Apr 15;263(11):5141-9.
The amino acid sequences of the alpha-crystallin A and B chains of the dogfish, Squalus acanthias, have been determined. Comparison with alpha-crystallins from other species reveals that charged amino acid replacements have been strongly avoided in the evolution of this lens protein. The homology of alpha-crystallins with the small heat shock proteins is pronounced throughout the major part of the proteins, starting from the position of the first intron in the alpha-crystallin genes, but is also detectable in the amino-terminal sequences of human, Xenopus, and Drosophila small heat shock proteins. In addition, a remarkable short sequence similarity is present only in the amino termini of dogfish alpha B and Drosophila HSP22. The Schistosoma egg antigen p40 turns out to have a tandemly repeated region of homology with the common sequence domain of alpha-crystallins and small heat shock proteins. Comparison of hydropathy profiles indicates the conservation of conformation of the common domains in these three families of proteins. Construction of phylogenetic trees suggests that the alpha A and alpha B genes apparently originated from a single ancestral small heat shock protein gene and indicates that introns have been lost during the evolution of the heat shock protein genes.
已确定了角鲨（Squalus acanthias）α-晶状体蛋白A链和B链的氨基酸序列。与其他物种的α-晶状体蛋白进行比较发现，在这种晶状体蛋白的进化过程中，带电荷氨基酸的替换被强烈避免。α-晶状体蛋白与小热休克蛋白在整个蛋白质的主要部分都有明显的同源性，从α-晶状体蛋白基因中第一个内含子的位置开始，但在人类、非洲爪蟾和果蝇小热休克蛋白的氨基末端序列中也可检测到。此外，仅在角鲨αB和果蝇HSP22的氨基末端存在显著的短序列相似性。血吸虫卵抗原p40被证明与α-晶状体蛋白和小热休克蛋白的共同序列结构域有串联重复的同源区域。亲水性图谱的比较表明这三类蛋白质中共同结构域的构象具有保守性。系统发育树的构建表明αA和αB基因显然起源于一个单一的祖先小热休克蛋白基因，并表明在热休克蛋白基因的进化过程中内含子已经丢失。
