Calcium Binding Protein 4 (CABP4)

CABP4 associated with the C-terminal domain of Ca(V)4.1 alpha-1 and shifted the activation of the channel to hyperpolarized voltages following cotransfection in human embryonic kidney cells.Like other CABP family members, the deduced CABP4 protein contains 4 EF-hand motifs.Human, bovine, mouse, and rat CABP4 are highly homologous in their C-terminal regions, but are less conserved in their N-terminal regions. Northern blot analysis of several human tissues and rat retina and brain detected 1.6- and 3.8-kb transcripts only in retina. RT-PCR of mouse tissues detected expression only in retina. In situ hybridization and immunocytochemical analysis of monkey retina detected Cabp4 only in photoreceptors. Analysis of mouse retina found Cabp4 in rod spherules and cone pedicles, where it colocalized with synaptic vesicle proteins.