ROLE OF HEME-BINDING PROTEINS IN HEPATIC HEME TRANSPORT

血红素向肝脏的转运和血红蛋白向肝脏的转运 结合珠蛋白是组织特异性的、受体介导的过程。结果, 具有生物价值的铁被保存下来，有毒血红素的积累 被阻止了。在这里提出的研究的目的是阐明这一角色 最近发现的一种血红素结合蛋白成分(HBC) 肝细胞的蓄积和降解。在这些过程中，亚铁血红素 最初与肝细胞质膜中的HBC结合后被转运到 它在内质网上被血红素加氧酶分解代谢的部位。至 为了达到这一目标，这种与血红素结合的膜蛋白将被分离并 并对其在肝脏血红素转运中的作用进行了研究。 具体目标是： 1.从兔肝细胞质膜中分离出HBC并进行鉴定。 其分子大小、亚基数量和类型(如果存在)和化学成分 构图； 2.用纯化的HBC制备抗HBC的单特异性多克隆抗体； 3.从亲和力和亲和力的角度表征血红素-血红蛋白复合体 血红素结合的化学计量以及所涉及的氨基酸残基 在装订方面； 4.研究HbC在血浆中的定位和分布。 膜脂双分子层； 5.开始评估Hbc在细胞内血红素转运中的作用 肝细胞采用脉冲追逐、亚细胞分离和 免疫沉淀技术。 除了延长对HBC作用机制的研究 正如正在进行的结果所表明的那样，HBC与其他 膜上的血红素结合蛋白，如在质膜中的那些 十二指肠粘膜细胞和Friend红白血病细胞及已发现的 与铁蛋白有关的研究将会被探索。

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.