Cloning and sequencing of pel gene responsible for CMCase activity from Erwinia chrysanthemi PY35

The phytopathogenic bacterium Erwinia chrysanthemi secretes multiple isozymes of plant cell wall disrupting enzymes such as pectate lyase and endoglucanase. We cloned genomic DNA from Erwinia chrysanthemi PY35, One of the E. coli XL1-Blue clones contained a 5.1-kb Bam HI fragment and hydrolyzed carboxymethyl cellulose and polygalacturonic acid. By subsequent subcloning, we obtained a 2.9-kb fragment (pPY100) that contained the pet gene responsible for CMCase and pectate lyase activities. The pel gene had an open reading frame (ORF) of 1,278 bp encoding 425 amino acids with a signal peptide of 25 amino acids. Since the deduced amino acid sequence of this protein was very similar to that of Pelt of E. chrysanthemi EC16, we concluded that it belonged to the pectate lyase family EC 4.2.2.2, and we designated it PelL1. Sequencing showed that the PelL1 protein contains 400 amino acids and has a calculated pi of 7.15 acid a molecular mass of 42,925 Da. The molecular mass of PelL1 protein expressed in E. coli XL1-Blue, as analyzed by SDS-PAGE, appeared to be 43 kDa. The optimum pH for its enzymatic activity was 9, and the optimum temperature was about 40 degrees C.