Pore-forming pyocin S5 utilizes the FptA ferripyochelin receptor to kill Pseudomonas aeruginosa

Abstract

Pyocins are toxic proteins produced by some strains of Pseudomonas aeruginosa that are lethal for related strains of the same species. Some soluble pyocins (S2, S3 and S4) were previously shown to use the pyoverdine siderophore receptors to enter the cell. The P. aeruginosa PAO1 pore-forming pyocin S5 encoding gene (PAO985) was cloned into the expression vector pET15b, and the affinity-purified protein product tested for its killing activity against different P. aeruginosa strains. The results, however, did not show any correlation with a specific ferripyoverdine receptor. To further identify the S5 receptor, transposon mutants were generated. Pooled mutants were exposed to pyocin S5 and the resistant colonies growing in the killing zone were selected. The majority of S5-resistant mutants had an insertion in the fptA gene encoding the receptor for the siderophore pyochelin. Complementation of an fptA transposon mutant with the P. aeruginosa fptA gene in trans restored the sensitivity to S5. In order to define the receptorbinding domain of pyocin S5, two hybrid pyocins were constructed containing different regions from pyocin S5 fused to the C-terminal translocation and DNase killing domains of pyocin S2. Only the protein containing amino acid residues 151 to 300 from S5 showed toxicity, indicating that the pyocin S5 receptor-binding domain is not at the N-terminus of the protein as in other Stype pyocins. Pyocin S5 was, however, unable to kill Burkholderia cenocepacia strains producing a ferripyochelin FptA receptor, nor was the B. cenocepacia fptA gene able to restore the sensitivity of the resistant fptA mutant P. aeruginosa strain.

A Natural ChimericPseudomonasBacteriocin with Novel Pore-Forming Activity Parasitizes the Ferrichrome Transporter

“…It typically concerns outer membrane proteins (OMPs) involved in the uptake of iron via siderophores: type I ferripyoverdine transporter FpvAI for pyocins S2, S4, and SD2 (17–19), type II ferripyoverdine transporter FpvAII for pyocin S3 (20), and ferripyochelin receptor FptA for pyocin S5 (21). Some S pyocins carry (almost) identical amino-terminal regions and basically differ only in their toxin-immunity module, emphasizing the peculiar modularity of these allelopathic molecules.…”

Structural and biophysical analysis of nuclease protein antibiotics

“…E-type colicins parasitize the vitamin B 12 receptor, BtuB, as their primary receptor in the outer membrane [9] and the Tol-Pal complex in the periplasm [5]. S-type pyocins S2 and S5 bind FpvA and FptA, respectively, which import siderophore-chelated iron [10,11]. How they translocate across the outer membrane is not known, although pyocin AP41, the receptor of which has yet to be identified, may translocate into cells via the Tol-Pal system [12].…”

Iron acquisition in the cystic fibrosis lung and potential for novel therapeutic strategies

“…Bakkal et al (2010) have reported that bacteriocins produced by Pseudomonas and Burkholderia strains have intra-and interspecies bacteriocin-like inhibition ability within the CF lung (Bakkal et al, 2010). Some of these bacteriocins, such as the Pseudomonas pyocin, share the same receptors as siderophores (Denayer et al, 2007;Elfarash et al, 2014) and therefore interfere with iron acquisition of their target host. It has also been demonstrated that P. aeruginosa can lyse Staphylococcus aureus using PqsA, a coenzyme ligase, to gain access to internalized iron (Mashburn et al, 2005).…”