Complexin (Cplx)3 and Cplx4, SNARE-complex-regulators of the Cplx family, have been proposed to be involved in the light adaptation of ribbon synapses by limiting synaptic vesicle (SV) recruitment and fusion, but how this Cplx effect is exerted is unknown. Focusing on light adaptation of rod photoreceptor ribbon synapses, we first applied gel-based proteomics to FACS-sorted cone and rod photoreceptor cells to show that Cplx4 is the predominant Cplx in mouse rod photoreceptors, a finding that was confirmed by immunocytochemistry and RT-qPCR analyses. To uncover the functional network linking Cplx4 to light adaptation, we developed a quantitative proteomic screen to identify proteins that specifically interact with the Cplx4-SNARE complex at rod photoreceptor ribbon synapses. For affinity purification, detergent-extracted mouse retina lysates were incubated with Cplx peptide-coupled beads. Eluted proteins were subjected to in-solution digestion and analyzed by label-free quantification. We identified the G protein Transducin, a key molecule of the phototransduction cascade and known to translocate from the photoreceptor outer segment to the presynaptic terminal in light, as a component of the Cplx4-SNARE complex.