STRUCTURE/FUNCTION RELATIONSHIPS OF DIPHTHERIA TOXIN A C

白喉毒素（DT）是一种典型的A-B毒素。 毒素的A链 含有酶活性（ADP-核糖基转移酶）。 DT是 突变化，试图单独抑制受体 结合或酶活性的毒素。 两次替换 发现白喉毒素A链（H21 G和G79 D）大大降低 毒素的酶活性似乎还没有改变 毒素的整体构象。 这两个DTA取代是 与野生型B链或已知的B链突变体组合， 减少8000的约束力。 具有单个或多个突变的毒素 在E.杆菌 这些突变体中的一些产生一种 中和免疫反应相当于或优于 市售化学类毒素白喉疫苗。

Diphtheria toxin (DT) is a classic A-B toxin. The A chain of the toxin contains the enzymatic activity (ADP-ribosyltransferase). DT was mutangenized in an attempt to individually inactivate either the receptor binding or enzymatic activities to the toxin. Two substitutions within the diphtheria toxin A chain (H21G and G79D) were found to greatly reduce the enzymatic activity of the toxin yet did not appear to alter the overall conformation of the toxin. These two DTA substitutions were combined with either wild type B-chain or a B-chain mutant known to an 8000 reduction in binding. Toxins having single or multiple mutations were expressed in E. coli. Several of these mutants produce a neutralizing immune response that is equivalent to or better than commercially available chemically toxoided diphtheria vaccine.