Cloning, sequence and expression of the pel gene from an Amycolata sp

The pel gene from an Amycolata sp. encoding a pectate lyase (EC 4.2.2.2) was isolated by activity screening a genomic DNA library in Streptomyces lividans TK24. Subsequent subcloning and sequencing of a 2.3 kb BamHI BglII fragment revealed an open reading frame of 930 nt corresponding to a protein of 29,660 Da. The overall G + C content for the coding region was 65%, with a strong G + C preference in the third (wobble) codon position (93%). A putative ribosome-binding site 5'-GGGAG-3' preceded the translational start codon by 7 base pairs. The Amycolata pectate lyase contains a signal peptide of 26 amino acids, that is cleaved after the sequence Ala-Thr-Ala. The size of the deduced protein as well as its N-terminal amino-acid sequence match the wild-type pectate lyase from the Amycolata sp. Expression of the pel gene in S. lividans TK24 resulted in high pectate lyase activity in the culture supernatant, concomitant with the appearance of a dominant protein band on a sodium dodecyl polyacrylamide gel at 30 kDa. No pectate lyase activity was detected in E. coli BL21 with the pel gene under the strong T7 promotor. The deduced amino-acid sequence showed 40% identity with PelE from Erwinia chrysanthemi and the pectate lyase from Glomerella cingulata. The Amycolata pectate lyase clearly belongs to the pectate lyase superfamily, sharing all functional amino acids and likely has a similar structural topology as Pels from Erwinia chrysanthemi and Bacillus subtilis.