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The rod outer segment ATP binding cassette (ABC) transporter protein (ABCR) plays an important role in retinal rod cells presumably transporting retinal. Genetic studies in humans have linked mutations in the ABCR gene to a number of inherited retinal diseases particularly Stargardt macular degeneration and age-related macular degeneration (ARMD). The ABCR protein is characterized by two nucleotide binding domains and two transmembrane domains, each consisting of six membrane-spanning helices. We have cloned and expressed the 376 amino acid (aa) C-terminal end of this protein (amino acid residues 1898−2273) containing the second nucleotide binding domain (NBD2) with a purification tag at its amino terminus. The expressed protein was found to be soluble and was purified using a rapid and high-yield single-step procedure. The purified protein was monomeric and migrated as a 43 kDa …