Weinberg R B, Patton C S
Department of Medicine, University of Texas Health Science Center, Houston 77225.
Biochim Biophys Acta. 1990 May 22;1044(2):255-61. doi: 10.1016/0005-2760(90)90311-k.
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.
我们研究了人载脂蛋白A-IV（apo A-IV）与人肝细胞质膜的结合情况。在存在和不存在25倍过量未标记apo A-IV的情况下，向肝质膜中添加浓度递增的放射性标记apo A-IV，结果显示与膜的饱和结合，解离常数（KD）为154 nM，最大结合量为1.6 ng/微克膜蛋白。该结合对温度不敏感，部分依赖钙，当apo A-IV被盐酸胍变性时或膜用链霉蛋白酶处理时结合被消除，而当apo A-IV掺入磷脂/胆固醇蛋白脂质体中时结合减少。在使用纯化载脂蛋白和分离脂蛋白的置换研究中，只有未标记的apo A-IV、apo A-I和高密度脂蛋白能有效地与放射性标记的apo A-IV竞争膜结合位点。我们得出结论，人apo A-IV对分离的人肝细胞质膜表现出高亲和力结合，这种结合是可饱和的、可逆的且具有特异性。
