Decoding channel pore dynamics mechanism in Anopheles gambiae Orco homotetramer.

MOTIVATION: Insect odorant receptors (iORs) essential for olfaction function as 7-transmembrane-domain (7TM) ion channels. iORs form tetrameric complexes that include a highly conserved odorant receptor co-receptor (Orco). Functional Orco homotetramers have also known to form ex vivo. Blocking Orco ex vivo and in vivo disrupts olfactory signalling, making it a promising target for functional intervention. Understanding its gating behaviour is critical for developing strategies to disrupt odour-guided behaviours in disease-vector insects. Thus, insights into the dynamic gating of the Anopheles gambiae Orco have implications on the rational design of vector-control strategies against malaria. We studied molecular dynamics (MD) simulations on homotetrameric AgamOrco models generated using template-based modelling (TBM) and AlphaFold3 (AF3), to investigate ligand-dependent pore dynamics. Agonist and antagonist bound systems were analysed to understand the ligand-dependent gating.

RESULTS: Our results show that apo and antagonistic IPC-bound AgamOrco homotetramer models remain in a stable, closed, and non-conductive state across both models. TBM, but not AF3, successfully captures agonistic VUAA1-induced activation, consistent with experimental observations, exhibiting asymmetric pore widening and conformational changes. Antagonist displacement simulations confirm IPC-mediated pore closure. Overall, the TBM AgamOrco model provides a reliable framework for structure-guided discovery of novel agents for control of insect pests and vector diseases.