Sequence of the algL gene of Pseudomonas aeruginosa and purification of its alginate lyase product

The alginate lyase-encoding gene (algL) of Pseudomonas aeruginosa was localized to a 1.7-kb EcoRI-Xba I fragment within the alginate biosynthetic gene cluster at 34 minutes on the chromosome. The nucleotide sequence of this DNA fragment revealed an ORF encoding a protein of M_r 40 885 which is transcribed in the same orientation as the other alg genes within the biosynthetic gene cluster. The predicted protein has a potential N-terminal signal peptide which is consistent with its proposed periplasmic location. The AlgL protein was overproduced in Escherichia coli and purified. The purified protein was shown to have alginate lyase activity. In addition, an algL insertion mutant of the mucoid P. aeruginosa 8830 was constructed. This mutant (alml) had a nonmucoid phenotype due to a polar effect on the transcription of an essential alg gene, algA. Thus, the algL gene is located within a region of the alginate biosynthetic gene cluster that appears to be non-essential for alginate production.