Nucleotide sequence analysis of the phosphomannose isomerase gene (pmi) of Pseudomonas aeruginosa and comparison with the corresponding Escherichia coli gene manA.

Phosphomannose isomerase (PMI) has been proposed to catalyze the first step of the alginic acid biosynthetic pathway in Pseudomonas aeruginosa. The nucleotide sequence of the P. aeruginosa pmi gene contained on a 2.0-kb BamHI-SstI DNA fragment has been determined. The gene was defined by the start and stop codons and by in vitro disruption of an open reading frame of 1440 bp corresponding to a polypeptide product with a predicted Mr of 52 860. This polypeptide displayed an apparent Mr of approx. 56 000 upon electrophoresis of a maxicell extract on sodium dodecyl sulfate-polyacrylamide gels. The codon utilization of the pmi gene was distinct in the wobble base preference and influenced by the high G + C content (66 mol%) of the P. aeruginosa DNA. Computer assisted matching analysis failed to demonstrate any significant homology at the nucleotide level between the P. aeruginosa pmi and Escherichia coli manA (pmi) genes. However, sequences homologous to the P. aeruginosa pmi gene were found in other Pseudomonas species, such as P. putida and P. mendocina, and in Azotobacter vinelandii, all capable of producing alginic acid.