Complementary DNA encoding the Na/Ca,K‐exchanger was isolated from bovine retina cDNA libraries. The complete full‐length cDNA is approximately 4 kb long and contains an open reading frame of 3597 bp. The deduced amino acid sequence corresponds to a protein of 1199 amino acids with a calculated molecular weight of approximately 130 kDa. Hydrophobicity analysis revealed the presence of two alternating sets of hydrophobic and hydrophilic domains. There also exists a hydrophobic region at the N‐terminus which may be part of a cleavable signal peptide. The protein shares limited sequence homology with the Na/Ca‐exchanger from cardiac sarcolemma. Northern blot analysis indicates that the approximately 6 kb transcript is highly specific for retinal tissue. Insect cells infected with recombinant baculovirus bearing the full‐length cDNA express a functional Na/Ca,K‐exchanger with an apparent relative molecular weight of approximately 210 kDa, as determined by Western blotting.

A major obstacle in the purification of membrane transport or receptor proteins is the requirement for a method of detection of the protein in question after solubilization 'This work was supported by the Deutsche Forschungsgemeinschaft (SFB 169 Projekt 0%) and a Leibniz-Programm Grant to Prof. Hartmut Michel.