Autoinducerbinding

Autoinducerbinding refers to the molecular interaction in which autoinducer signals bind to receptor proteins to regulate gene expression in bacterial quorum sensing. Autoinducers accumulate in the environment as population density increases, and binding to cognate receptors triggers signal transduction and transcriptional responses.

In Gram-negative bacteria, the predominant signals are acyl-homoserine lactones (AHLs). AHLs diffuse across membranes; once inside or upon binding to cytosolic LuxR-type receptors, the ligand induces conformational changes that promote receptor dimerization and binding to target DNA, activating or repressing transcription of quorum-sensing–regulated genes, such as those controlling bioluminescence, virulence, and biofilm formation. The LuxI-LuxR circuit is a classic example, as in Vibrio fischeri where the LuxR–AHL complex activates the lux operon.

In Gram-positive bacteria, peptide autoinducers are typically detected by membrane-associated histidine kinases in two-component systems. Binding of the autoinducing peptide to the receptor triggers autophosphorylation and a phosphotransfer cascade that modulates response regulators and gene expression, including virulence and competence programs. The Staphylococcus aureus agr system exemplifies this mode, where the autoinducing peptide binds AgrC, triggering phosphorylation of AgrA and regulation of numerous virulence genes.

A second class, autoinducer-2 (AI-2), supports interspecies signaling and is detected by multiple receptors, such as LuxP–LuxQ or Lsr transport and processing systems in different bacteria. Binding affinity and signaling outcomes depend on concentration, environmental context, and receptor architecture.

Understanding autoinducerbinding informs strategies to disrupt quorum sensing, with potential anti-virulence and anti-biofilm therapies.