PURIFICATION OF THE ACIDIC PECTATE LYASE AND NUCLEOTIDE-SEQUENCE OF THE CORRESPONDING GENE (PELA) OF ERWINIA-CHRYSANTHEMI STRAIN-3937

The pelA gene from Erwinia chrysanthemi strain 3937, which encodes the acidic pectate lyase, PLa, has been sequenced and characterized. The structural gene consists of a 1179 bp open reading frame encoding a polypeptide of 41555 Da, which includes an N-terminal signal peptide. The deduced amino acid sequence shows a protein very similar to some PLs already sequenced. Cloning of the pelA gene behind the lacZ promoter of the vector pTZ19R allowed overexpression of PLa into a derivative of strain 3937 deleted of the other pel genes. The mature protein was obtained in milligram amounts from the supernatant of this strain and at homogeneous purity after two purification steps. Its biochemical properties were similar to those of other PLs. Polyclonal antibodies raised against the purified PLa cross-reacted with the basic pectate lyase PLd, but not with PLe. The role of Pta in pathogenicity is discussed.