Figure 3

Genomic organization of PAPI-2 and exoU . Genomic organization of the Pseudomonas aeruginosa strain, PAO1, is shown (upper left). PAO1 contains 5,570 open reading frames (ORFs) in its 6.3-Mb genome. The type III secretion regulatory region (25.5 kb), known as the exoenzyme S regulon, contains 36 genes in the five operons. Genes encoding the type III secretory toxins exoS, exoT, and exoY, but not exoU, are scattered throughout the genome. exoU is located in an insertional pathogenic gene cluster known as PAPI-2 [26],[30]. PAPI-2 has 14 ORFs, including exoU and spcU, in a 10.7-Kb region (upper right). exoU has an ORF of 2,074 base pairs and a promoter region with an ExsA binding motif (TAAAAAA) at -74 (lower middle). The primary sequence of ExoU is 682 amino acids and contains an N-terminal secretory leader sequence, which shares similarity with ExoS and ExoT, and a patatin-like phospholipase domain with a catalytic dyad (Ser142 and Asp344), and a C-terminal DUF885 domain associated with a proposed ubiquitin binding domain. The patatin-like domain of ExoU has a structure similar to cytosolic phospholipase A₂ (cPLA₂), calcium-independent PLA₂ (iPLA₂), and patatin from plants. Red letters with highlighted backgrounds indicate a perfect match. Blue letters indicate a partial match for amino acid sequences among four PLA₂ proteins. PAPI, Pseudomonas aeruginosa pathogenicity island.