Human erythrocyte band 7.2b is preferentially labeled by a photoreactive phospholipid

A head-group modified, photoreactive analog of phosphatidylethanolamine, N-([I-125]iodo-4-azidosalicylamidyl)-1,2-dilauryl-sn-glycero-3-phosphatidylethanolamine ([I-125]-N-ASA-DLPE). has been used in photoaffinity labeling studies of proteins of the human erythrocyte membrane. [I-125]-N-ASA-DLPE was shown to be preferentially incorporated into a protein with an apparent molecular weight of 31 kDa. protein sequencing and immunoprecipitation were used to identify this protein as the erythrocyte membrane protein, and 7.2b or stomatin. A sulphydryl-reactive ligand, 4-hydroxy-3-(iodo-[I-125])-N-[2-(2-pyridinyldithio)ethyl]-benzenepropanamide ([I-125]-PDA), was also shown to preferentially label band 7.2b, We propose that band 7.2b may act as a site of transbilayer reorientation of membrane phospholipids. (C) 1996 Academic Press, Inc.