Identification of XcpP domains that confer functionality and specificity to the Pseudomonas aeruginosa type II secretion apparatus.
Gram-negative bacteria have evolved several types of secretion mechanisms to release proteins into the extracellular medium. One such mechanism, the type II secretory system, is a widely conserved two-step process. The first step is the translocation of signal peptide-bearing exoproteins across the inner membrane. The second step, the translocation across the outer membrane, involves the type II secretory apparatus or secreton. The secretons are made up of 12-15 proteins (Gsp) depending on the organism. Even though the systems are conserved, heterologous secretion is mostly species restricted. Moreover, components of the secreton are not systematically exchangeable, especially with distantly related microorganisms. In closely related species, two components, the GspC and GspD (secretin) family members, confer specificity for substrate recognition and/or secreton assembly. We used Pseudomonas aeruginosa as a model organism to determine which domains of XcpP (GspC member) are involved in specificity. By constructing hybrids between XcpP and OutC, the Erwinia chrysanthemi homologue, we identified a region of 35 residues that was not exchangeable. We showed that this region might influence the stability of the XcpYZ secreton subcomplex. Remarkably, XcpP and OutC have domains, coiled-coil and PDZ, respectively, which exhibit the same function but that are structurally different. Those two domains are exchangeable and we provided evidence that they are involved in the formation of homomultimeric complexes of XcpP.
Gérard-Vincent
Manon
M
Laboratoire d'lngénierie des Systèmes Macromoléculaires, UPR9027, IBSM/CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
Robert
Viviane
V
Ball
Geneviève
G
Bleves
Sophie
S
Michel
Gérard P F
GP
Lazdunski
Andrée
A
Filloux
Alain
A
D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005816:Genetic Complementation Test; D026901:Membrane Transport Proteins; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; C105759:OutC protein, bacteria; D011993:Recombinant Fusion Proteins; C089840:XcpP protein, Pseudomonas aeruginosa