CD4+ LIPID BILAYERS - A MODEL FOR HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 COAT PROTEIN-BINDING

gpl20, the coat glycoprotein of the human immunodeficiency virus type 1 (HIV1) binds to a molecule on the surface of a class of T-lymphocytes, CD4, which is also the receptor for major histocompatibility complex class Il (MHCII). To study the events that follow the interaction of gpl20 with CD4, we have incorporated CD4 into lipid bilayers and recorded the electrical changes which occur after the addition of gpI20. Interaction of gpl20 to CD4-containing bilayers induces multistate ion-permeable channels with a maximum conductance of 380-400 picosiemens. When CD4+ bilayers were preexposed to either MHCII or to OKT4A antibody, no channels were formed after the addition of gpl20. These results indicate that CD4+-containing bilayers bind gpl20, MHCII, and OKT4A, that binding of gpl20 produces ion-permeable channels, and that CD4+ bilayers can be used to assay for gp120 in the solution bathing the bilayer.