Involved in the negative feedback regulation of the light-activated signaling cascade in photoreceptors through a calcium-mediated process. Interacts with tetrapeptide ligand located in C-terminal sequence of 3 key components of the visual cascade, tethering them and forming a macromolecular signaling phototransduction complex. Interacts with the C-terminus of trp, and with norpA and inaC to form the inaD signaling complex. Interacts with Fkbp59, which together with trpl, rhodopsin and calmodulin may also be part of the inaD complex. Expressed in rhabdomeres of the compound eyes and ocelli. Second PDZ domain is a type I PDZ domain that tethers type I PDZ ligand inaC by interaction with its C-terminus. Phosphorylated by inaC.