Structure of an insect gustatory receptor.

Area of Science:

• Structural biology
• Insect chemosensation
• Molecular mechanisms of ion channels

Background:

• Gustatory Receptors (GRs) are crucial for insect chemosensation but their structures remain elusive.
• Understanding GR structure is vital for developing novel pest and disease vector control methods.

Approach:

• Determined the experimental structures of Bombyx mori Gr9 (BmGr9), a fructose-gated cation channel, in both apo and ligand-bound states.
• Utilized structural data to compare BmGr9 with distantly related insect Olfactory Receptors (ORs).
• Performed structure-based sequence alignments to identify conserved patterns in GR ligand-binding pockets.

Key Points:

• BmGr9 forms a tetrameric channel, distinct from ORs in its ligand-binding pocket characteristics.
• Fructose binding induces conformational changes, opening the ion channel via helix S7b movements.
• The BmGr9 ligand-binding pocket is larger, solvent-accessible, and utilizes helix S5 for fructose interaction, unlike ORs.

Conclusions:

• The study provides the first experimental structures of an insect GR, elucidating the molecular basis of fructose binding and ion channel gating.
• Distinct structural features of BmGr9 compared to ORs highlight divergent evolutionary paths in chemosensory receptor families.
• Conservation patterns in ligand-binding pockets offer insights into GR subfamily specificity for diverse ligand classes.