Fatty acid acylation of membrane skeletal proteins in human erythrocytes

Fatty acid acylation of membrane proteins was studied on human erythrocytes by measuring incorporation of [3H]palmitate at different specific radioactivities. A 55 kDa polypeptide within the band 4.5 region was the main acceptor protein for acylation by fatty acids (palmitate, stearate, oleate), while other polypeptides (80, 65, 48, 30 kDa) incorporated [3H]palmitate slowly, in substoichiometric amounts. Integral membrane proteins were preferentially fatty acid acylated. Skeletal membrane proteins were, however, poorly labeled. Neither purified ankyrin nor band 4.1 protein were fatty acid acylated in human erythrocytes. On the other hand, label associated with high molecular weight skeletal proteins resisted low and high ionic strength extractions, and was extracted selectively by urea [corrected] along with a small subpopulation of spectrin which was also tightly associated with the membrane.