Structural determinants driving homoserine lactone ligand selection in thePseudomonas aeruginosaLasR quorum-sensing receptor.McCready, A.R., Paczkowski, J.E., Henke, B.R., Bassler, B.L.
(2019) Proc Natl Acad Sci U S A 116: 245-254
- PubMed: 30559209
- DOI: https://doi.org/10.1073/pnas.1817239116
- Primary Citation of Related Structures:
- PubMed Abstract:
Quorum sensing is a cell-cell communication process that bacteria use to orchestrate group behaviors. Quorum sensing is mediated by signal molecules called autoinducers. Autoinducers are often structurally similar, raising questions concerning how bacteria distinguish among them ...
Quorum sensing is a cell-cell communication process that bacteria use to orchestrate group behaviors. Quorum sensing is mediated by signal molecules called autoinducers. Autoinducers are often structurally similar, raising questions concerning how bacteria distinguish among them. Here, we use the Pseudomonas aeruginosa LasR quorum-sensing receptor to explore signal discrimination. The cognate autoinducer, 3OC 12 homoserine lactone (3OC 12 HSL), is a more potent activator of LasR than other homoserine lactones. However, other homoserine lactones can elicit LasR-dependent quorum-sensing responses, showing that LasR displays ligand promiscuity. We identify mutants that alter which homoserine lactones LasR detects. Substitution at residue S129 decreases the LasR response to 3OC 12 HSL, while enhancing discrimination against noncognate autoinducers. Conversely, the LasR L130F mutation increases the potency of 3OC 12 HSL and other homoserine lactones. We solve crystal structures of LasR ligand-binding domains complexed with noncognate autoinducers. Comparison with existing structures reveals that ligand selectivity/sensitivity is mediated by a flexible loop near the ligand-binding site. We show that LasR variants with modified ligand preferences exhibit altered quorum-sensing responses to autoinducers in vivo. We suggest that possessing some ligand promiscuity endows LasR with the ability to optimally regulate quorum-sensing traits.
Howard Hughes Medical Institute, Chevy Chase, MD 20815.