GENETIC ENGINEERING OF SHORT CONSENSUS REPEAT ELEMENTS

短共识或补体重复序列(SCR)是一种模块化蛋白质 通常在不同的基因外显子中编码的结构单位。SCR 最近成为人们极感兴趣的焦点，因为他们 在一系列明显无关的蛋白质中被发现 包括凝血系统的一个组成部分，牛痘 病毒编码蛋白，淋巴因子受体，3细胞黏附 受体，以及至少10种补体蛋白。SCR范围为60-70 氨基酸长度，它们含有4或6个保守的半胱氨酸，以及 有一个涉及大约40%残基的共识序列。他们 可能是独立的结构单元，在概念上类似于 免疫球蛋白结构域，由一个基本的骨架结构组成 哪些序列变体与特定功能相关 叠加在一起。 SCR的功能(S)在许多情况下是未知的，但它们的广泛 分布表明，它们满足关键的结构和 职能角色。他们已经在最广泛的研究 补体蛋白。在大多数，也许是所有这些情况下，他们的 主要功能是与补体成分C3和C4结合，以及 也许是次要的，以提供线性、延伸的结构。装订 含Scr的蛋白质对C3和C4都是必不可少的 两条补体途径的激活和调节。装订 含Scr的蛋白质对C3和C4具有特异性；具有明显的 结合C3或C4的SCRs。 这项拨款建议使用基因工程方法来解剖 SCR与补体成分C3和C4之间的相互作用。在……里面 特别是，我们计划在SCR和C3中识别氨基酸 和C4，它们是结合所必需的，也是结合特异性所必需的。 作为这种相互作用的模型，我们将研究小鼠的结合 C4与小鼠C4结合蛋白结合，小鼠C3与小鼠H因子结合。 所提出的计划的长期目标是在 氨基酸序列水平控制结合的规则 SCR的特异性及其蛋白质的结构特征 目标。这一理解应该为具体情况提供线索。 以及这些结构基元在其他(特别是非 补体)蛋白质，并可能提供对 可溶性和可溶性的相互作用和进化关联性 血流中的膜结合蛋白。能够改变 这些蛋白质的特异性或反应性很可能具有 对治疗剂的最终发展的影响。

The short consensus or complement repeat (SCR) is a modular protein structural unit that is usually encoded in distinct gene exons. SCRs have recently become the focus of substantial interest because they have been found in a wide range of apparently unrelated proteins including a component of the blood coagulation system, a vaccinia virus-encoded protein, a lymphokine receptor, 3 cellular adhesion receptors, and at least 10 complement proteins. SCRs range from 60-70 amino acids in length, they contain 4 or 6 conserved cysteines, and have a consensus sequence involving about 40% of the residues. They are likely to be independent structural units, similar in concept to immunoglobulin domains, consisting of a basic framework structure onto which sequence variations related to specific functions are superimposed. The function(s) of SCRs are in many cases unknown but their wide distribution suggests that they fulfill crucial structural and functional roles. They have been most extensively studied in the complement proteins. In most and perhaps all of these cases, their primary function is to bind to complement components C3 and C4, and perhaps secondarily to provide a linear, extended structure. Binding of SCR-containing proteins to both C3 and C4 are essential for activation and regulation of the two complement pathways. The binding of SCR-containing proteins to C3 and C4 is specific; with distinct SCRs binding to either C3 or C4. This grant proposes to use genetic engineering methods to dissect the interaction between SCRs and complement components C3 and C4. In particular we plan to identify amino acids within SCRs, and within C3 and C4 which are necessary for binding, and for binding specificity. As models of this interaction, we will examine the binding of murine C4 to murine C4-binding protein, and of murine C3 to murine factor H. The long-term goal of the program proposed is to understand at the amino acid sequence level the rules governing the binding specificities of SCRs and the structural features of their protein targets. This understanding should provide clues to the specificities and functions of these structural motifs in other (especially non- complement) proteins, and may provide a more unified understanding of the interactions and evolutionary relatedness of both soluble and membrane-bound proteins in the bloodstream. The ability to alter the specificities or reactivities of these proteins is likely to have implications for the eventual development of therapeutic agents.