Purification, characterization and cDNA cloning of a novel lectin from the jellyfish Nemopilema nomurai.

A lectin (designated NnL) from a jellyfish Nemopilema nomurai was purified by ion-exchange chromatography followed by affinity chromatography. The apparent molecular mass of NnL was 28kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing and nonreducing conditions. NnL agglutinated horse erythrocytes, the gram-positive bacterium Bacillus subtilis and gram-negative bacterium Escherichia coli K12. The hemagglutinating activity of NnL was inhibited by N-acetyl-D-galactosamine N-acetylneuraminic acid and N-glycolylneuraminic acid. Bovine submaxillary mucin was the potent inhibitor of the hemagglutinating activity of NnL among the glycoproteins tested. cDNA cloning of NnL revealed that its primary structure contained part of a fibrinogen-like domain. The deduced amino acid sequence of NnL showed no significant sequence identities to other known lectins. On the other hand NnL showed high sequence identity to a predicted protein of the sea anemone Nematostella vectensis suggesting that NnL may belong to a novel lectin family in metazoans. This is the first report to describe the purification characterization and cDNA cloning of a jellyfish lectin.

Molecular cloning of calnexin and calreticulin in the Pacific oyster Crassostrea gigas and its expression in response to air exposure.

Calnexin (CNX) and calreticulin (CRT) are endoplasmic reticulum (ER) chaperones. CNX is a type I transmembrane protein and CRT is a soluble CNX homologue. In the ER, CNX and CRT are important for Ca(2+) homeostasis and protein maturation. Here, we describe the full-length cDNA of the first mollusk CNX (cgCNX) and a second mollusk CRT (cgCRT) from the oyster Crassostrea gigas. CgCNX, containing 3255bp, was composed of a 1764bp open reading frame (ORF) that encodes a 588-amino acid protein. CgCRT, containing 1727bp, was composed of a 1242bp ORF that encodes a 414-amino acid protein. CgCNX and cgCRT contains an N-terminal 21- and 16-amino acid sequence, respectively, which is characteristic of a signal sequence. At the C-terminus, cgCRT also contains the KDEL (-Lys-Asp-Glu-Leu) peptide motif suggesting that cgCRT localizes in the ER. Northern blot analysis showed that both cgCNX and cgCRT mRNAs are induced by air exposure. The expression patterns of cgCNX mRNA differed from those of cgCRT during air exposure. This suggests that these two molecular chaperones have different roles in the response to air exposure.