Cloning and Characterization of the Pectate Lyase III Gene of Erwinia carotovora Er

A pectate lyase gene III (pel III) of Erwinia carotovora Er was cloned. The gene was expressed independently of a vector promoter in both E. carotovora Er and Escherichia coli. The pel III product was largely excreted in the culture medium of E. carotovora Er, while the product was only exported to the periplasmic space and was not excreted in the medium of E. coli. Nucleotide sequence analysis of pel III disclosed an open reading frame of 1,122 bp encoding a protein of 374 amino acids. The deduced amino acid sequence contained the N-terminal 30 amino acid sequence from the purified pectate lyase III (PL III) indicating the presence of a 22-amino-acid signal peptide. A putative ribosome-binding site was found to be 9 bp upstream of the start codon. The location of pel III was about 5.6 kb downstream of pel I. The PL III showed 80% homology in the amino acid sequence with the PL I of E. carotovora Er.9)