Cloning and characterization of a CMCase gene, celB, of Erwinia carotovora subsp. carotovora LY34 and its comparison to celA

Abstract

The phytopathogenic Erwinia carotovora subsp. carotovora (Ecc) LY34 secretes multiple isozymes of the plant cell wall-disintegrating enzyme endoglucanase. We isolated a second cel gene encoding CMCase in Ecc LY34. A 3.7 kb fragment was subcloned to generate pLYCB100 (celB). The structural organization of the celB gene consists of an open reading frame (ORF) of 792 bp encoding 264 264 amino acid residues with a calculated molecular weight of 29,890 Da The predicted amino acid sequence of CelB is very similar to that of CelS of another Ecc strain, SCRI193, but completely different from that of the CelA of Ecc LY34. It belongs to the glycosyl hydrolase family 12 based on amino acid sequence similarities. It is optimally active at pH 6.8 with an optimal temperature of about 50 degrees C. The CMCase activity of CelB is about 60% of that of CelA.