The present invention provides a system and method for expressing functional ABC (ATP-binding cassette) proteins, from the ABCA subfamily, in a host cell. A system comprises two or more expression vectors each comprising a nucleic acid molecule encoding one or more domains of an ABC transporter gene and a means for expressing the nucleic acid molecule. Each expression vector of the system includes a nucleic acid molecule that encodes a domain that is functionally complementary to domains contained in the other expression vectors of the system but when taken together comprise the full ABC transporter gene. Co-transfection of the expression vectors into a host cell provides co-expression of each of the domains of the protein which associate to form an ABC transporter protein having functional characteristics of the full-length protein.