THE NUCLEOTIDE-SEQUENCE OF THE BETA-GLUCOSIDASE GENE FROM CELLVIBRIO-GILVUS

A gene encoding beta-glucosidase from Cellvibrio gilvus, a cellobiose-producing bacterium, was cloned into Escherichia coli and sequenced. The structural gene consisted of 2565 bp encoding 854 amino acid residues with a characteristic signal peptide. A typical promoter sequence and SD region were located upstream of the initiation ATG codon. A sequence (180 amino acids) having high homology with those of beta-glucosidases from several microorganisms was found in the deduced amino acid sequence of C. gilvus beta-glucosidase. This sequence contains the aspartic acid residue which was found to be an active site residue in Aspergillus wentii beta-glucosidase A3. The beta-glucosidase gene of C. gilvus contains a high amount (69.4%) of G + C. These bases are localized not in the 3rd position of the codon, as is usually observed in G + C-rich genes, but rather in the lst position. This result in a peptide which contains an extremely high amount (48%) of four amino acids (Pro, Ala, Arg, Gly) coded by CCN, GCN, CGN, and GGN.