Crystal structure and characterization of coiled-coil domain of the transient receptor potential channel PKD2L1

► Crystal structure of a segment of the PKD2L1 cytoplasmic regulatory domain (CRD). ► Structure reveals a trimeric coiled coil in the predicted oligomerization region. ► Trimerization driven by central β-branched residues and stabilized by a salt bridge. ► Mutation of central residues converts high-affinity trimeric CRD to monomer. ► Monomer binds Ca2+ with WT-affinity, loses significant α-helicity upon ligand removal.