title: Crystallins of the octopus lens. Recruitment from detoxification enzymes.
abstract: The eye lens crystallins of the octopus Octopus dofleini were identified by sequencing abundant proteins and cDNAs. As in squid, the octopus crystallins have subunit molecular masses of 25-30 kDa, are related to mammalian glutathione S-transferases (GST), and are encoded in at least six genes. The coding regions and deduced amino acid sequences of four octopus lens cDNAs are 75-80% identical, while their non-coding regions are entirely different. Deduced amino acid sequences show 52-57% similarity with squid GST-like crystallins, but only 20-25% similarity with mammalian GST. These data suggest that the octopus and squid lens GST-like crystallin gene families expanded after divergence of these species. Northern blot hybridization indicated that the four octopus GST-like crystallin genes examined are lens-specific. Lens extracts showed about 40 times less GST activity using 1-chloro-2,4-dinitrobenzene as substrate than liver extracts of the octopus, indicating that the major GST-like crystallins are specialized for a lens structural role. A prominent 59-kDa crystallin polypeptide, previously observed in octopus but not squid and called omega-crystallin (Chiou, S.-H. (1988) FEBS Lett. 241, 261-264), has been identified as an aldehyde dehydrogenase. Since cytoplasmic aldehyde dehydrogenase is a major protein in elephant shrew lenses (eta-crystallin; Wistow, G., and Kim, H. (1991) J. Mol. Evol. 32, 262-269) the octopus aldehyde dehydrogenase crystallin provides the first example of a similar enzyme-crystallin in vertebrates and invertebrates. The use of detoxification stress proteins (GST and aldehyde dehydrogenase) as cephalopod crystallins indicates a common strategy for recruitment of enzyme-crystallins during the convergent evolution of vertebrate and invertebrate lenses. For historical reasons we propose that the octopus GST-like crystallins, like those of the squid, are called S-crystallins.
authors.affiliation: Laboratory of Molecular and Developmental Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: S I
authors.initials: SI
authors.lastname: Tomarev
authors.forename: R D
authors.initials: RD
authors.lastname: Zinovieva
authors.forename: J
authors.initials: J
authors.lastname: Piatigorsky
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D015152:Blotting, Northern; D003001:Cloning, Molecular; D003459:Crystallins / Q000235:genetics* / Q000302:isolation & purification; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D049832:Decapodiformes / Q000235:genetics; D015723:Gene Library; D005982:Glutathione Transferase / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000235:genetics*; D007908:Lens, Crystalline / Q000502:physiology*; D008099:Liver / Q000201:enzymology; D008969:Molecular Sequence Data; D005810:Multigene Family; D049831:Octopodiformes / Q000235:genetics*; D009838:Oligodeoxyribonucleotides; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012689:Sequence Homology, Nucleic Acid
chemical_list: D003459:Crystallins; D007527:Isoenzymes; D009838:Oligodeoxyribonucleotides; D012313:RNA; D004247:DNA; D000444:Aldehyde Dehydrogenase; D005982:Glutathione Transferase