Octopus S-crystallins with endogenous glutathione S-transferase (GST) activity: sequence comparison and evolutionary relationships with authentic GST enzymes

Abstract

S-Crystallin is a major protein present in the lenses of cephalopods (octopus and squid). To facilitate the cloning of this crystallin gene, cDNA was constructed from the poly(A)+ mRNA of octopus lenses, and amplified by PCR for nucleotide sequencing. Sequencing of 10 of 15 positive clones coding for this crystallin revealed three distinct S-crystallin isoforms with 61-64% identity in nucleotide sequences and 42-58% similarity in amino acid sequences when compared with homologous crystallins in squid lenses. These charge-isomeric crystallins also show between 26 and 33% amino acid sequence identity to four major classes of glutathione S-transferase (GST), a major detoxification enzyme present in most mammalian tissues. For further analysis, expression of one of the S-crystallin cDNAs was carried out in the bacterial expression system pQE-30, and the S-crystallin protein produced in Escherichia coli was purified to homogeneity to determine the enzymic properties. We found that the expressed octopus S-crystallin possessed much lower GST activity than the authentic GSTs from other tissues. Sequence comparison and construction of phylogenetic trees for S-crystallins from squid and octopus lenses and various classes of GSTs revealed that S-crystallins represent a multigene family which is structurally related to Alpha-class GSTs and probably derived from the ancestral GST by gene duplication and subsequent multiple mutational substitutions.

The Molecular Refractive Function of Lens γ-Crystallins

“…S-crystallin sequences have also been determined for two octopus species 70,71 . Like in squid, they are related to GST (20–25% sequence similarity 70 ), and exhibit a 48–58% sequence similarity with squid SL20 and 42–80% similarity between the octopus species 71 .…”

“…Like in squid, they are related to GST (20–25% sequence similarity 70 ), and exhibit a 48–58% sequence similarity with squid SL20 and 42–80% similarity between the octopus species 71 . We calculated a high dn/dc , with values of ~0.197 ml/g (Table 3).…”

Transcriptome Profiling of Selectively Bred Pacific Oyster Crassostrea gigas Families that Differ in Tolerance of Heat Shock

“…4a) mRNA decreased after 6 h, and based on the RT-QPCR data was greater in low-surviving families at 6 h after stress. The protein S-crystallin is derived from glutathione S-transferase and is a major protein of vertebrate and invertebrate eye lenses that appears to lack enzymatic function (Chiou et al 1995; Tomarev and Piatigorsky 1996; Chuang et al 1999; Blanchette et al 2007). As with most of the probes included on the microarray, it is possible that the probe for this S-crystallin EST hybridized with mRNA from multiple genes including glutathione S-transferase, leading to the discrepancy between the microarray data and the RT-PCR data.…”

A delta-class glutathione transferase from the Chinese mitten crab Eriocheir sinensis: cDNA cloning, characterization and mRNA expression

“…To date, many novel classes of GST sequences have been identified and classified from non-mammalian organisms [18]. A few of the aquatic invertebrates in which GST has been studied include bivalve mollusks (Atactodea striata) [19], gastropods (Bulinus truncates) [20], marine shrimp (Litopenaeus vannamei) [21], crayfish (Macrobrachium vollenhovenii) [22], clams (Raditapes decussates) [23], squids (Ommastrephes sloani pacificus) [24], octopi (Octopus vulgaris) [25], and blue mussels (Mytilus edulis) [26]. Most of these in vivo studies focused on purification and/or biochemical measurement of total GST or different GST isoforms.…”