Biochemical characterization of human Thy-1.

The human Thy-1 homologue (p25) was characterized biochemically for amino acid composition, sequence and carbohydrate content. Two other forms of the human Thy-1 molecule were detected and partially characterized. A 40,000 mol.wt. molecule (p40) is the dimer of p25 and its formation is increased by the presence of sodium dodecyl sulphate (SDS). The second form of 16,000 mol.wt. (p16) appears to be a cryptic or breakdown form of p25. Comparison of the amino acid compositions of p25, p40 and p16 isolated from MOLT-3 cells, with that deduced from the nucleotide sequence of the gene coding for part of the putative T cell antigen receptor, also from MOLT-3 cells, shows that the Thy-1 homologue is distinct from, but evolutionary related to, one of the putative T cell antigen receptor polypeptide chains.