Transition State Analysis of Diphtheria Toxin

描述（由申请人提供）：ADP-核糖基化细菌外毒素是 这些蛋白质是导致各种严重人类疾病的原因， 霍乱、百日咳和白喉。白喉毒素（DT）催化 NAD+的ADP核糖基部分共价转移到双苯二甲酰胺残基， 真核细胞延伸因子2（eEF-2）。这种共价转移使 eEF-2，使其不能多肽链延长，抑制 蛋白质合成并最终杀死靶细胞。的目标 这一建议是为了确定过渡国家的结构， 白喉毒素对eEF-2的ADP-核糖基化反应动力学同位素测定 放射性标记的NAD+类似物的KIE效应。过渡态分析 由白喉毒素催化的反应将导致更好的 了解这种酶，并应提供目标结构， 作为抑制剂的新型过渡态类似物的设计。

DESCRIPTION (provided by applicant): ADP-ribosylating bacterial exotoxins are proteins that are responsible for various severe human diseases such as cholera, pretussis, and diphtheria. Diphtheria toxin (DT) catalyzes the covalent transfer of the ADPribosyl moiety of NAD+ to a dipthamide residue in eukaryotic elongation factor 2 (eEF-2). This covalent transfer inactivates eEF-2, rendering it incapable of polypeptide chain elongation, inhibiting protein synthesis and eventually killing the target cells. The objective of this proposal is to determine the transition state structure of ADP-ribosylation of eEF-2 by diphtheria toxin by measuring kinetic isotope effects (KIEs) with radiolabeled NAD+ analogues. Transition state analysis of the reaction catalyzed by diphtheria toxin will result in a better understanding of this enzyme and should provide target structures for the design of novel transition state analogues as inhibitors.