Binding of human apolipoprotein A-IV to human hepatocellular plasma membranes.
We have investigated the binding of human apolipoprotein A-IV (apo A-IV) to human hepatocellular plasma membranes. Addition of increasing concentrations of radiolabeled apo A-IV to hepatic plasma membranes, in the presence and absence of a 25-fold excess of unlabeled apo A-IV, revealed saturation binding to the membranes with a KD of 154 nM and a binding maximum of 1.6 ng/microgram of membrane protein. The binding was temperature-insensitive, partially calcium-dependent, abolished when apo A-IV was denatured by guanidine hydrochloride or when the membranes were treated with Pronase and decreased when apo A-IV was incorporated into phospholipid/cholesterol proteoliposomes. In displacement studies using purified apolipoproteins and isolated lipoproteins, only unlabeled apo A-IV, apo A-I and high-density lipoproteins effectively competed with radiolabeled apo A-IV for membrane binding sites. We conclude that human apo A-IV exhibits high-affinity binding to isolated human hepatocellular plasma membranes which is saturable, reversible and specific.
Weinberg
R B
RB
Department of Medicine, University of Texas Health Science Center, Houston 77225.
Patton
C S
CS
D001054:Apolipoproteins A / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D006801:Humans; D008099:Liver / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D013696:Temperature
D001054:Apolipoproteins A; C022205:apolipoprotein A-IV; D002118:Calcium