Cloning and sequencing of a molluscan endoâβâ1,4âglucanase gene from the blue mussel, Mytilus edulis
2001
Xu, Bingze | Janson, JanâChrister | Sellos, Daniel
Using polymerase chain reaction, cloning and sequencing techniques, a complementary DNA encoding a low molecular mass cellulase (endoâ1,4âβâdâglucanase, ECâ3.2.1.4) has been identified in the digestive gland of the marine mussel, Mytilus edulis. It contains a 5′ untranslated region, a 633ânucleotide ORF encoding a 211 aminoâacid protein, including a 17 aminoâacid signal peptide and a complete 3′ untranslated region. At the Câterminal end of the purified mature protein, a 13 aminoâacid peptide is lacking in comparison to the protein sequence deduced from the ORF. This peptide is probably removed as a consequence of postâtranslational amidation of the Câterminal glutamine. The endoglucanase genes have been isolated and sequenced from both Swedish and French mussels. The coding parts of these two sequences are identical. Both genes contain two introns, the positions of which are conserved. However the length of the introns are different due to base substitutions, insertions or deletions showing the existence of interspecies length polymorphism. The percentage of similarity for the introns of the two gene sequences is 96.9%. This is the first time a molluscan cellulase is characterized at DNA level. Amino acid sequenceâbased classification has revealed that the enzyme belongs to the glycosyl hydrolase family 45 [B. Henrissat (Centre de Recherches sur les Macromolecules Végétales, CNRS, Joseph Fourier Université, Grenoble, France), personal communication]. There is no cellulose binding domain associated with the sequence.
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