Identification and analysis of cDNA clones encoding CD53. A pan-leukocyte antigen related to membrane transport proteins.

CD53 is a human cell-surface Ag expressed exclusively by nucleated cells of hemopoietic origin. In this work a cDNA clone encoding the CD53 Ag was isolated from a COS cell-expression library. The sequence of the cDNA predicts a protein of 219 residues bearing four putative membrane-spanning hydrophobic domains. Sequence analysis shows that CD53 is related to three other recently described molecules: a melanoma Ag, ME491; a B cell Ag, CD37; and the broadly distributed hemopoietic cell Ag S5.7. Comparison of NH2-terminal protein sequence of OX44 rat Ag and CD53 suggest that CD53 is the human homologue of OX44. In addition, CD53 is distantly related to Escherichia coli lac Y permease, a type III integral membrane protein that ferries lactose into the bacterial cell. CD53 transcripts increase in prevalence after mitogenic stimulation, suggesting that the protein may be involved in the transport of factors essential for cell proliferation.