STRUCTURE AND FUNCTION OF B12-BINDING PROTEINS

B12 结合蛋白的结构和功能

• 批准号: 3483388
• 负责人: ROBERT H ALLEN
• 金额: $ 31.32万
• 依托单位: UNIVERSITY OF COLORADO DENVER
• 依托单位国家: 美国
• 财政年份: 1977
• 资助国家: 美国
• 起止时间: 1977-07-01 至 1990-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3483388
• 关键词: DNA binding protein; antineoplastics; binding proteins; chemical structure function; chromatography; cobamide; cofactor; gastric juice; gastrointestinal nutrient absorption; gel electrophoresis; glycoproteins; human tissue; intestinal mucosa; intrinsic factor; iodination; ion transport; iron; laboratory rabbit; methionine adenosyltransferase; myeloproliferative neoplasm; nitrous oxide; nutrition related tag; pancreas enzyme; protein metabolism; radioimmunoassay; radiotracer; reticulocytes; small intestines; swine; transferrin; transport proteins; ultracentrifugation; vitamin B12 transport defect; vitamin metabolism

The objectives are to elucidate the structural and functional properties of cobalamin (Cb1, vitamin B12)-binding proteins which are involved in the cellular uptake and utilization of Cb1, and to apply this information to a number of clinical situations. We will study the functional significance of the observation that Cb1 is preferentially bound by R protein in gastric juice and is not transferred to instrinsic factor until after the R protein moiety is partially degraded by pancreatic enzymes in the small intestine. We will further define the role of intrinsic factor and transcobalamin II in the ileal absorption of Cb1 and study the essentially undefined mechanisms by which Cb1 is released from cells, with particular emphasis on its release from ileal absorptive cells and hepatocytes. We will study the regulation of the two mammalian Cb1-dependent enzymes, L-methylmalonyl-CoA mutase and methionine synthetase, and elucidate the pathways involved in the conversion of Cb1 to its coenzyme forms, Ado-Cb1 and CH3-Cb1. We will study the metabolism of methylmalonic acid and investigate the possibility that it has an important and overlooked biochemical function. We will further define the ileal and neutrophil-hepatocyte mechanisms that prevent the intestinal absorption and tissue dissemination of potentially toxic Cb1 analogues of bacterial origin and determine if these Cb1 analogues are present in blood and tissues in various diseases. We will study the properties and origins of a new class of Cb1 analogues that have recently been observed in human and animal blood and tissues, in multivitamin-mineral pills and animal chows, and in animals exposed to nitrous oxide. We will determine the biologic activities and inhibitory properties of a variety of Cb1 analogues, use them to develop an animal model of Cb1 deficiency, and investigate their activity as chemotherapeutic agents against malignant cells. Methylmalonic acid, homocysteine, and methionine will be assayed in various blood samples using assays based on capillary gas chromatography-mass spectrometry. These assays enable the activities of the two mammalian Cb1-dependent enzymes to be assessed in vivo and will be utilized in studies involving patients with marked and mild Cb1 deficiency, various levels of serum Cb1, various neuropsychiatric diseases, and subjects exposed to nitrous oxide in the work place.

目的是阐明的结构和功能特性， 钴胺素（Cb 1，维生素B12）结合蛋白，它们参与了 细胞对Cb 1的摄取和利用，并将此信息应用于 临床情况的数量。 我们将研究观察到的功能意义，即Cb 1是 优先与胃液中的R蛋白结合，不转移 直到R蛋白部分被部分降解后， 被小肠中的胰腺酶消化。 我们将进一步定义 内因子和转钴胺素II在回肠吸收中的作用 研究Cb 1释放的基本未定义的机制 从细胞，特别强调其释放从回肠吸收 细胞和肝细胞。 我们将研究两种哺乳动物Cb 1依赖性酶的调节， L-甲基丙二酰辅酶A和甲硫氨酸合成酶，并阐明 参与将Cb 1转化为辅酶形式的途径， 和CH 3-Cb 1。 我们将研究甲基丙二酸的代谢， 调查它有一个重要的和被忽视的可能性， 生化功能 我们将进一步确定回肠和嗜肝细胞的机制， 防止潜在的肠道吸收和组织传播 细菌来源的毒性Cb 1类似物，并确定这些Cb 1 类似物存在于各种疾病的血液和组织中。 我们将 研究一类新的Cb 1类似物的性质和起源， 最近在人类和动物血液和组织中观察到， 多种维生素-矿物质药丸和动物咀嚼物，以及暴露于 一氧化氮 我们将确定生物活性和抑制 各种Cb 1类似物的性质，用它们来开发动物 Cb 1缺陷模型，并研究其作为化疗药物的活性 针对恶性细胞的药剂。 甲基丙二酸、同型半胱氨酸和蛋氨酸将在不同的 使用基于毛细管气相色谱-质谱的分析的血液样品 光谱法 这些测定使两种哺乳动物的活性 将在体内评估Cb 1依赖性酶，并将用于 涉及明显和轻度Cb 1缺乏患者的研究，各种 血清Cb 1水平、各种神经精神疾病和受试者 在工作场所接触一氧化二氮