Figure 7.

Alternative splicing of Ca²⁺ channel β subunit A domains. Splicing patterns of exons identified to date that code for the A domains of β subunits 1–4 (for review, see Takahashi et al., 2003; Foell et al., 2004). The diagram indicates that multiple A domain splicing variants have been identified for β subunits: β₁, one variant; β₂, five variants; β₃, one variant; and β₄, two variants. Exons are numbered relative to the positions of the seven exons on the β₂ gene (for additional explanation of the relatedness of each exon, see Discussion). The first three amino acids (exons 1, 2, 4, 5, 6, and 7) or last two amino acids (exon 3) of individual exons are specified. The coding sequences for the SH3 (B) domain begin downstream of exon 7.