CONSTRAINING BETA-TURN STRUCTURE IN MODEL IMMUNOGENS

球状蛋白质分子主要由β-折叠和α-折叠组成。 链轨迹急剧变化分离的螺旋二级结构 在分子表面有四个残基β转角或更大的环。 这些Betaturn和环结构通常可以在蛋白质中识别 序列，有助于二级结构预测和在 潜在线型多肽抗体表位的鉴定 制作。而识别完整蛋白质的抗肽抗体 在一些情况下已经制备了链，从而产生了单克隆 抗体对折叠蛋白的亲和力通常较低，而这些折叠蛋白是 推导了人工合成的多肽免疫原序列。提出了一项协议 使用第二种蛋白质(葡萄球菌核酸酶)作为“宿主”来约束 通过将客体多肽免疫原结合到天然结构中 在适当的位置测序成杂交蛋白。工作将继续进行 在两个杂交蛋白质系统上发展这一方法并了解其 在结构和物理方面的成功或失败。 过去三年的结果表明，有一个强大的 贝塔转弯的顺序和类型之间的关系，可以是 对球状蛋白上下文的显性影响。调查将会 继续定义氨基酸序列和氨基酸序列之间的关系 贝塔转弯类型。这些实验应该会在我们的 预测球状蛋白中的Betaturn位置的能力，并应定义 上述杂合蛋白的蛋白质工程设计原则和 总的来说，其他新的蛋白质分子。核磁共振和X射线结晶学 将继续进行实验，努力通过以下方式定义物理基础 哪种顺式多肽键在VI型β转折中更受青睐 葡萄球菌核酸酶。这一系统提供了一个观察 氨基酸序列对两个β转弯平衡的影响 球状蛋白质表面的类型。遗传学和结晶学 分析将继续定义与类型I‘一致的序列 核酸酶中的β-转折及其物理和结构基础 序列首选项。

Globular protein molecules are largely composed of beta-sheet and alpha- helical secondary structures separated by sharp changes in chain trajectory at four residue beta-turns or larger loops on the surface of the molecule. These betaturn and loop structures can often be recognized in protein sequences, aiding in secondary structure prediction and in the identification of potential linear peptide epitopes for antibody production. While antipeptide antibodies which recognize a full protein chain have been prepared in a number of cases, the resulting monoclonal antibodies often have a low affinity for the folded protein from which the synthetic peptide immunogen sequence was derived. A protocol was proposed to use a second protein (staphylococcal nuclease) as a "host" to constrain the "guest" peptide immunogen into a native structure by incorporating that sequence into a hybrid protein at an appropriate site. Work will continue on two hybrid protein systems to develop this method and to understand its success or failure in structural and physical terms. Results during the last three years indicate that there is a strong relationship between the sequence and type of a beta-turn which can be dominant over globular protein context effects. Investigations will continue to define the relationship between amino acid sequence and beta-turn type. These experiments should provide an improvement in our ability to predict betaturn sites in globular proteins and should define protein engineering design principles for the hybrid proteins above and other new protein molecules in general. NMR and x-ray crystallography experiments will continue in an effort to define the physical basis by which a cis peptide bond is favored in a type VI beta-turn of staphylococcal nuclease. This system provides an opportunity to observe the influence of amino acid sequence on the equilibrium between two beta-turn types on the surface of a globular protein. A genetic and crystallographic analysis will continue to define sequences consistent with a type I' beta-turn in nuclease, and the physical and structural basis for these sequences preferences.