Comparison of transmembrane topologies of Ca²⁺channelγ_1–5 subunits predicted by the TMpred program (Hofmann and Stoffel 1993). Positive TMpred values (y-axis, ×1000) indicate likely membrane spanning segments. Amino acid position is shown on the x-axis. All five γ subunit isoforms are predicted to contain four transmembrane domains with amino and carboxyl termini located intracellularly.