Alpha-2-Macroglobulin of Invertebrates

α-2-巨球蛋白是一种血浆蛋白，存在于所有种类的脊椎动物中，具有广谱蛋白酶抑制剂的功能。这项拟议的研究将调查一种来自马蹄蟹的α-2-巨球蛋白的结构和功能。本实验室已经获得了广泛的多肽序列信息和抗-2-巨球蛋白的抗血清，这些信息将被用来从一个发展到凝胶变形细胞Poly(A)+RNA的CDNA文库中分离和测序全长的cDNA.与脊椎动物具有大量的血浆蛋白水解酶抑制物不同，α-2-巨球蛋白是唯一存在于河蟹血浆中的蛋白水解酶抑制物，这将有助于其在体内的功能鉴定。这项拟议的研究将调查α-2-巨球蛋白参与受体介导的蛋白酶清除途径的可能性。α-2-巨球蛋白还参与河豚血浆中的一个细胞溶解系统，该系统可能与脊椎动物的补体系统同源。将对这个系统进行表征，确定参与的分子，并描述它们的作用顺序和细胞溶解机制。这项研究代表了无脊椎动物补体样细胞溶解系统的第一个分子特征，应该会提供关于这一重要的免疫样防御系统的有价值的信息。%多细胞生物体有一系列不同的防御策略，限制了它们对潜在病原体破坏的敏感性。这些防御机制通常涉及血液中的细胞和可溶性因子。这些血液因素中最古老的一种是血浆蛋白，即α-2-巨球蛋白。这种分子广泛存在于从无脊椎动物到人类的各种动物中。阿尔法-2-巨球蛋白似乎有两种常见的功能，一种是捕获血液或细胞表面的酶，否则可能会通过消化其他蛋白质来破坏这些酶；第二种是作为特定生化连锁反应的一部分，该反应的功能是杀死入侵的病原体或外来细胞。本研究的目的是研究相对原始的马蹄蟹的α-2-巨球蛋白的结构和功能。这项研究的结果将有助于理解自然界中发现的各种防御机制，也可能有助于揭示高等生物防御分子的功能。

The alpha-2-macroglobulins are plasma proteins that are present in all classes of vertebrates and that function as broad-spectrum protease inhibitors. The proposed research will investigate the structure and function of a form of alpha-2-macroglobulin from the horseshoe crab, Limulus polyphemus. This laboratory has obtained extensive peptide sequence information and antisera to Limulus alpha-2-macroglobulin which will be used to isolate and sequence the full length cDNA from a CDNA library developed to the poly (A)+ RNA of the Limulus amebocyte. In contrast to vertebrates, which possess a large number of plasma protease inhibitors, alpha-2- macroglobulin is the only protease inhibitor in the plasma of Limulus, which should facilitate its functional characterization in vivo. The proposed research will investigate the possibility that alpha-2-macroglobulin participates in a receptor-mediated clearance pathway for proteases. Alpha-2-macroglobulin also participates in a cytolytic system in the plasma of Limulus that may be homologous to the vertebrate complement system. This system will be characterized, the participating molecules identified, and their sequence of action and mechanism of cytolysis characterized. This study, which represents the first molecular characterization of a complement-like cytolytic system in an invertebrate, should yield valuable information concerning this important immune-like defense system. %%% Multicellular organisms have a varied array of defense strategies that limit their susceptibility to damage by potential pathogens. These defense mechanisms generally involve cells and soluble factors of the blood. One of the most ancient of these blood factors is the plasma protein, alpha-2-macroglobulin. This molecule is found in a wide range of animals from invertebrates to humans. Alpha-2-macroglobulin appears to have two general types of function, one as a trap for enzymes in the blood or on cell surfaces that might otherwise do damage by digesting other proteins, and the second is as a part of a specific biochemical chain reaction that functions to kill invading pathogens or foreign cells. The purpose of this research is to characterize the structure and function of the alpha-2-macroglobulin from the horseshoe crab, Limulus, a relatively primitive animal. The results of this research will contribute to understanding of the diverse array of defense mechanisms found in nature, and may also shed light on the functioning of the defense molecules of higher organisms.