CRYSTAL STRUCTURE DETERMINATION OF CATALYTIC ANTIBODIES

描述：催化抗体的结构-功能研究旨在 重点抓好三个制度。(1)经诱导产生的抗体48G7 磷酸盐过渡态(TS)类似物，并催化 相应的酯和碳酸盐。这一系统代表了 研究过渡的最简单和最普遍的抗体催化反应 状态稳定和催化。此外，生殖系基因已经被 克隆和表达，为免疫进化的研究奠定了基础 催化作用。亲和力成熟对TS类似物功能的影响 结合和催化可以分析和解释为 成熟品系(48G7)和种系的三维结构 抗体。此外，在大肠杆菌中的高水平表达系统将 允许对活性部位和体细胞进行系统的诱变研究 突变的残留物。(2)抗AZ-28抗体 主席状TS类似物，并催化相应的氧合 重新编排。实际上没有任何一种酶能催化这种周环 除分支酸变位酶外，重排的机制 尽管进行了广泛的结构和机制研究，但这一点仍然不清楚。 因此，对这种生物的详细结构和功能研究 催化剂可能有助于深入了解对催化剂的要求 化学转化。此外，一个家庭的可用性 催化这种单分子反应的抗体可能有助于阐明 那些对活动至关重要的因素。(3)抗体28B4.2 催化硫醚的氧化反应生成相应的 亚硫醚。这是第一个使用非生物催化剂的生物催化剂 活性的“辅因子”，即高碘酸根离子，代替亚铁血红素和 黄素辅因子由相应的酶使用。属性的kcat值。 抗体和酶具有可比性，这表明这一策略可能会 用廉价的化学辅因子取代昂贵的辅因子。 对该抗体的结构和作用机制有详细的了解 活性部位结构与半抗原结构的关系可以 建议推广，并可能允许对抗体进行工程 增强的立体选择性或可允许对抗体进行修饰以 其他反应，如二硫键的形成。

DESCRIPTION: Structure-function studies of catalytic antibodies are to focus on three systems. (1) The antibody 48G7 which was elicited to a phosphonate transition-state (TS) analogue and catalyzes the hydrolysis of the corresponding esters and carbonates. This system represents one of the simplest and most prevalent antibody-catalyzed reactions to study transition state stabilization and catalysis. Moreover, the germline genes have been cloned and expressed, permitting the study of the immunological evolution of catalysis. The functional effects of affinity maturation on TS analogue binding and catalysis can be analyzed and interpreted in terms of the three-dimensional structures of both the mature (48G7) and germline antibodies. In addition, a high level expression system in E. coli will allow a systematic mutagenesis study of both the active site and somatically mutated residues. (2) The antibody AZ-28 which was elicited against a chairlike TS analogue and catalyzes the corresponding oxy-Cope rearrangement. There are virtually no enzymes that catalyze such pericyclic rearrangements with the exception of chorismate mutase, the mechanism of which remains unclear despite extensive structural and mechanistic studies. Consequently, detailed structure-function studies of this biological catalyst may shed insight into the requirements for catalysis of the chemical transformation. Moreover, the availability of a family of antibodies that catalyze this unimolecular reaction may help to elucidate those factors essential for activity. (3) The antibody 28B4.2 which catalyzes the oxygenation reaction of a thioether to the corresponding sulfoxide. This was the first biological catalyst to use an abiological "cofactor" for activity, i.e. a periodate ion, in place of the heme and flavin cofactors used by the corresponding enzymes. The kcat values for the antibody and enzymes are comparable, suggesting that this strategy may allow the replacement of expensive cofactors with inexpensive chemical cofactors. A detailed understanding of the structure and mechanism of this antibody and the relationship of the active site structure to hapten structure may suggest generalizations and may allow engineering of antibodies with enhanced stereoselectivities or may permit modification of the antibody to other reactions such as disulfide bond formation.