We have isolated a cDNA clone coding for rat Thy-1 antigen from a rat thymocyte cDNA library. The 549 base pairs insert includes the complete coding region of a mature Thy-1 polypeptide of 142 amino acids, 31 amino acids longer than the previously reported glycoprotein sequence. These 31 amino acids contain an extremely hydrophobic region of 26 uncharged amino acids which apparently represent the transmembrane segment that allows for integration within the membrane. The presence of this additional protein segment will solve most of the enigmas regarding the properties of the C-terminal region of Thy-1 antigen.
