Independent regulation of MucD, an HtrA-like protease in Pseudomonas aeruginosa, and the role of its proteolytic motif in alginate gene regulation

Expression of mucD, encoding a homologue of the HtrA(DegP) family of endoserine proteases, was investigated in Pseudomonas aeruginosa. Expressed from the algT-mucABCD operon, MucD was detected in mucoid (FRD1) and nonmucoid (PAO1) parental strains and also when polar insertions were placed upstream in algT or mucB. A transcriptional start site for a mucD promoter (PmucD) was mapped within mucC. Expression of single-copy mucD217, encoding MucD altered in the protease motif (S217A), was defective in temperature resistance and alginate gene regulation.