AN UNUSUAL FORM OF LIPID LINKAGE TO THE CD45 PEPTIDE

Some protein kinases and phosphatases are myristoylated on their amino terminus, which perhaps contributes to subcellular localization or regulation. Glycoprotein CD45, a hematopoietic tyrosine phosphatase, was examined for fatty acid content. The CD45 protein incorporated [3H]myristate, but little [3H]palmitate. The label was not metabolized and reincorporated into amino acids or saccharides, as revealed by peptide maps of CD45 labeled with [3H]myristate, 14C-labeled amino acids, [ 35S]methionine, or 125I, and glycosidase treatments, respectively. The myristate label was resistant to mild alkaline medianolysis and was found in fatty acid and sphingosine, indicating an unusual form of lipid attachment to CD45.