Murphy T M, Mills S E
J Bacteriol. 1969 Mar;97(3):1310-20. doi: 10.1128/jb.97.3.1310-1320.1969.
The reactive surface structures of alpha subunits of tryptophan synthase from Escherichia coli, Shigella dysenteriae, Salmonella typhimurium, Aerobacter aerogenes, and Serratia marcescens were compared by measuring (i) their reactivities in micro-complement-fixation assays with antibodies directed specifically to E. coli wild-type alpha subunit, (ii) their reactivities in enzyme neutralization assays with the same antibodies, and (iii) their binding affinities for tryptophan synthase beta(2) subunits. The enzymes from the four heterologous species cross-reacted in the microcomplement-fixation assays with the anti-E. coli alpha subunit antibodies, each to a different degree. However, neutralization titers of the antibodies reacting with the various alpha subunits were comparatively similar, and the beta(2) subunit-binding and -stimulating abilities of the alpha subunits were even more closely alike. The results suggested that the tertiary structure of the beta(2) subunit-binding site of the alpha subunit has been conserved, relative to the rest of the molecule, during the evolutionary divergence of the species of Enterobacteriaceae.
通过测量以下各项，比较了来自大肠杆菌、痢疾志贺氏菌、鼠伤寒沙门氏菌、产气气杆菌和粘质沙雷氏菌的色氨酸合酶α亚基的反应表面结构：（i）它们在微量补体结合试验中与特异性针对大肠杆菌野生型α亚基的抗体的反应性；（ii）它们在酶中和试验中与相同抗体的反应性；（iii）它们对色氨酸合酶β(2)亚基的结合亲和力。来自这四种异源物种的酶在微量补体结合试验中与抗大肠杆菌α亚基抗体发生交叉反应，程度各不相同。然而，与各种α亚基反应的抗体的中和效价相对相似，并且α亚基的β(2)亚基结合和刺激能力甚至更为相似。结果表明，在肠杆菌科物种的进化分歧过程中，相对于分子的其余部分，α亚基的β(2)亚基结合位点的三级结构得到了保守。
