Structure of Leu-2/T8 as deduced from the sequence of a cDNA clone.

We have determined the primary structure of the Leu-2/T8 T lymphocyte differentiation antigen from the complete nucleotide sequence of a cDNA clone. The protein consists of a classical signal peptide, two external protein domains, a hydrophobic transmembrane segment, and a highly charged intracytoplasmic tail. The N-terminal external domain of the mature protein is homologous to immunoglobulin and T cell receptor variable regions. Protein structural predictions suggest that this domain can indeed fold like an immunoglobulin domain. The Leu-2/T8 protein has no segment that is homologous to a constant region. However, the membrane-proximal domain appears to serve as a hinge. These studies indicate that Leu-2/T8 is another member of the immunoglobulin supergene family.