Figure 4

A novel pathogenicity island encoding the diphtheria toxin in C. ulcerans . (A) Genome Browser view of the novel PAI of KL251. The upper panel indicates the lower local GC content of the PAI compared with the remaining C. ulcerans genome. The borders of the lower GC regions delimit the novel genomic region. The regions up- and downstream of the PAI are conserved in other Corynebacterium species and are flanked by a direct and near perfect 100 bp repeat, which includes parts of the tRNA-Arg and thereby results in a pseudo-tRNA gene downstream of the PAI. Both tRNA-Arg and the pseudo-tRNA are labeled with black arrows. Among the predicted proteins of the PAI are two putative integrases/transposases and two additional predicted DNA binding proteins and the DT. CDS, coding sequence. (B) Predicted domains of the proteins. The locations of the proteins in the PAI are indicated by the numbers in (A). (1) A predicted integrase/recombinase enzyme. (2) A putative transcriptional regulator carrying a DUF955 domain with unknown function. The DUF955 domain carries a H-E-X-X-H motif and is suspected to be catalytically active as metallohydrolase [64]. The helix-turn-helix (HTH)-like domain is similar to the HTH-like domain of the Cro/C1 and lambda repressor. (3) A non-cytoplasmic protein of unknown function with predicted signal peptide. (4) Hypothetical peptide, which is most likely not expressed. (5) Protein with a DUF955 domain of unknown function. (6) Possible homologous protein to a putative insertion element (IS): homeodomain (HO)-like domain including a HTH-domain. Predicted to bind a specific DNA sequence and suspected to be a transcriptional regulator [65]. (7) Putative transposases composed of a DNA-binding HTH domain and an integrases/ribonuclease H domain. (8) DT precursor as known from other C. ulcerans and C. diphtheriae isolates.