Fig. 1

TpsA/CdiA protein domains in P. aeruginosa. A The domains of a CdiA from the N-terminus are the conserved two-partner secretion (TPS) transport domain, filamentous hemagglutinin domain 1 (FHA-1), receptor-binding domain (RBD), Tyr/Pro-enriched (YP) domain, second FHA domain (FHA-2), the pre-toxin (TD) domain, and the C-terminus toxin domain (CdiA-CT). Figure was modified from a diagram by Allen et al. [31]. A conserved region found at TpsA N-terminal termed “TPS domain” is necessary for interaction to and secretion by TpsB. Secretion of P. aeruginosa N-terminal domain (1–360 aa) of proteins TpsA1 and TpsA2 (TpsA-NT) expressed in E. coli was confirmed by immunoblot analysis of culture supernatants collected from different clones with anti-Histidine tag antibody. C1, C2, C3, C4 are clones expressing and secreting recombinant protein TpsA-NT (31 kDa) in E. coli BL21 (DE3). P, represents plasmid pET29b + backbone in E. coli BL21 (DE3). B Phylogenetic tree of TPS domains of TpsA NT proteins. The tree shows the subdivision of TpsA proteins into two different families Fha30-like proteins and HMW1-like proteins. Phylogenetic trees were constructed using online tool phylogeny.fr (http://phylogeny.lirmm.fr/). N terminal amino acid residues of TpsA proteins (TpsA1 to 6) of P. aeruginosa were compared with H. influenzae HMW1 and HxuA proteins; B. pertussis FHA protein; S. marcescens ShlA protein; P. mirabilis HpmA protein and E. coli CdiA protein. N-terminal domain is anchored to the bacterial surface and C-terminal proteins are exposed in TpsA1/CdiA1 and TpsA2/CdiA2 proteins