ROLE OF HEME-BINDING PROTEINS IN HEPATIC HEME TRANSPORT

血红素结合素和血红蛋白向肝脏的转运 触珠蛋白是组织特异性的、受体介导的过程。 因此，在本发明中， 生物学上有价值的铁是保守的，有毒血红素的积累是 防止。 本研究的目的是阐明 最近发现的血红素结合蛋白成分（HBC） 通过肝细胞积累和降解。 在这些过程中，血红素 最初与肝细胞质膜中的HBC结合， 它在内质网中被血红素加氧酶催化的位点。 到 为了达到这个目的，这种血红素结合膜蛋白将被分离， 特征，并检查其在肝血红素转运中的功能。 具体目标是： 1.从兔肝细胞膜中分离HBC，并对其进行表征 其分子大小、亚基的数量和类型（如果存在）以及化学性质 组成; 2.用纯化的HBC制备抗HBC的单特异性多克隆抗体; 3.以表征血红素-HBC复合物的亲和力， 血红素结合的化学计量以及所涉及的氨基酸残基 装订; 4.研究HBC在等离子体中的取向和分布 膜脂双层; 5.开始评估HBC在细胞内血红素转运中的作用， 肝细胞采用脉冲追踪，亚细胞分级， 免疫沉淀技术。 除了扩大对HBC作用机制的研究外， 如持续的结果所示，HBC与其他 膜血红素结合蛋白，如在质膜中的那些血红素结合蛋白， 十二指肠粘膜细胞和Friend红白血病细胞以及那些发现 与铁蛋白的关系。

The transport to the liver of heme by hemopexin and of hemoglobin by haptoglobin are tissue-specific, receptor-mediated processes. As a result, biologically valuable iron is conserved and accumulation of toxic heme is prevented. The aim of the research proposed here is to elucidate the role of a recently-discovered heme-binding protein component (HBC) in heme accumulation and degradation by liver cells. During these processes heme bound initially to HBC in the hepatocyte plasma membrane is transported to its site of catabolism by heme oxygenase in the endoplasmic reticulum. To attain this goal, this heme-binding membrane protein will be isolated and characterized, and its function in hepatic heme transport examined. The specific aims are: 1. to isolate the HBC from rabbit liver plasma membrane and characterize its molecular size, number and type of subunits (if present) and chemical composition; 2. to use purified HBC to raise monospecific polyclonal antibodies to HBC; 3. to characterize the heme-HBC complex with respect to the affinity and stoichiometry of heme binding as well as the amino acid residues involved in binding; 4. to investigate the orientation and distribution of HBC in the plasma membrane lipid bilayer; 5. to begin to assess the role of HBC in intracellular heme transport by liver cells employing pulse-chase, subcellular fractionation and immunoprecipitation techniques. In addition to extending the examination of the mechanism of action of HBC as indicated by on-going results, the relationship of HBC with other membrane heme-binding proteins such as those in the plasma membrane of duodenal mucosal cells and of Friend erythroleukemia cells and those found in association with ferritin will be explored.