Figure 2. Predicted TRP structure and the phototransduction that leads to activation of TRP and TRPL.

A) Electroretinogram (ERG) recordings from trp⁺ (w¹¹¹⁸) and trp³⁴³ mutant flies (performed by Dr. Zijing Chen). B) Predicted structure of the Drosophila TRP channel. The channel contains six transmembrane domains, with the pore loop located between the 5^th and 6^th transmembrane domains. The N-terminal region contains four ankyrin repeat domains and a coiled coil domain, and the C-terminal tail contains a TRP domain, calmodulin (CaM) binding site, and an INAD binding site. C) Model of Drosophila phototransduction. Light capture by rhodopsin initiates a G^q/PLC signaling cascade that culminates in activation of the TRP and TRPL channels and influx of cations. Abbreviations: 1-MAG, monoacylglycerol; 2-MAG, 2-monoacylglycerol; DAG, diacylglycerol; FA, saturated fatty acid; IP₃, inositol 1,4,5-trisphosphate; PIP₂, phosphatidylinositol 4,5-bisphosphate; MAG, monoacylglycerol; P, pore loop indicated in TRP; PUFA, polyunsaturated fatty acid.