Exploring the 'N-terminal arm' & 'Convex surface' Binding Interfaces of the T3SS Chaperone-Translocator Complexes from P. Aeruginosa

One infection method widely used by many gram-negative bacteria involves a protein nanomachine called the Type Three Secretion System (T3SS). The T3SS enables the transportation of bacterial toxins via a proteinaceous channel that directly links the cytosol of the bacteria and host cell. The channel from the bacteria is completed by a translocon pore formed by two proteins named the major and minor transloca-tors. Prior to pore formation, the translocator proteins are bound to a small chaperone within the bacterial cytoplasm. This interaction is crucial to effective secretion. Here we investigated the specificity of the bind-ing interfaces of the translocator-chaperone complexes from Pseudomonas aeruginosa via the selection of peptide and protein libraries based on its chaperone PcrH. Five libraries encompassing PcrH's N -terminal and central a-helices were panned, using ribosome display, against both the major (PopB) and minor (PopD) translocator. Both translocators were shown to significantly enrich a similar pattern of WT and non-WT sequences from the libraries. This highlighted key similarities/differences between the interactions of the major and minor translocators with their chaperone. Moreover, as the enriched non-WT sequences were specific to each translocator, it would suggest that PcrH can be adapted to bind each translocator individually. The ability to evolve such proteins indicates that these molecules may pro-vide promising anti-bacterial candidates. & COPY; 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecom-mons.org/licenses/by/4.0/).

Automated summary

Many gram-negative bacteria use a protein nanomachine called the Type Three Secretion System (T3SS) to infect. This system transports bacterial toxins using a proteinaceous channel that links the bacteria and host cell. In this study, the specificity of the binding interfaces of the translocator-chaperone complexes from Pseudomonas aeruginosa was investigated.