Function of the hydrophobic transmembrane portion of Thy-1 antigen

Thy-1 antigen is anchored in the cell membrane by glycophosphatidyl inositol linkages instead of hydrophobic protein domains. The hydrophobic portion of Thy-1 antigen is cleaved by putative "transamidase." Mutated genes were constructed by using site-directed mutagenesis. One mutant gene codes Thy-1 antigen lacking carboxy terminal amino acids from 112Cys to 143Leu including cell membrane binding amino acid 112Cys. The other mutant gene codes Thy-1 antigen lacking from 124Trp to 143Leu that includes leucine core portion. DNA transfection analysis and Northern blot analysis revealed that hydrophobic portion of Thy-1 antigen is essential to express Thy-1 molecule onto the cell surface.