Dogfish α-crystallin sequences. Comparison with small heat shock proteins and Schistosoma egg antigen

W. W. De Jong, J. A.M. Leunissen, P. J.M. Leenen, A. Zweers, M. Versteeg

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The amino acid sequences of the α-crystallin A and B chains of the dogfish, Squalus acanthias, have been determined. Comparison with α-crystallins from other species reveals that charged amino acid replacements have been strongly avoided in the evolution of this lens protein. The homology of α-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 α-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 αB and Drosophila HSP22. The Schistosoma egg antigen p40 turns out to have a tandemly repeated region of homology with the common sequence domain of α-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 αA and αB 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.

Original languageEnglish
Pages (from-to)5141-5149
Number of pages9
JournalJournal of Biological Chemistry
Issue number11
Publication statusPublished - 15 Apr 1988
Externally publishedYes


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