Interaction of receptor for intrinsic factor-cobalamin complex with synthetic and brush-border lipids

The intestinal receptor for intrinsic factor-cobalamin complex integrates preferentially with cationic liposomes in such a way that its ligand binding sites are exposed to proteases and to antibody to the receptor. After integration the receptor could be solubilized from the liposomes by detergents and chaotropic salts. Kinetically, the brush-border and the liposome-bound receptor behaved similarly, and Triton X-100 had no effect either on Ka or Vmax, suggesting the absence of any effects of a lipid domain on ligand binding activity. However, acidic phospholipids caused inhibition when added to the receptor-ligand assay system in the absence of liposomes.