Merritt E A, Sixma T K, Kalk K H, van Zanten B A, Hol W G
Department of Biological Structure SM-20, University of Washington, Seattle 98195.
Mol Microbiol. 1994 Aug;13(4):745-53. doi: 10.1111/j.1365-2958.1994.tb00467.x.
The galactose-binding site in cholera toxin and the closely related heat-labile enterotoxin (LT) from Escherichia coli is an attractive target for the rational design of potential anti-cholera drugs. In this paper we analyse the molecular structure of this binding site as seen in several crystal structures, including that of an LT:galactose complex which we report here at 2.2 A resolution. The binding surface on the free toxin contains several tightly associated water molecules and a relatively flexible loop consisting of residues 51-60 of the B subunit. During receptor binding this loop becomes tightly ordered by forming hydrogen bonds jointly to the GM1 pentasaccharide and to a set of water molecules which stabilize the toxin:receptor complex.
霍乱毒素以及大肠杆菌中与之密切相关的不耐热肠毒素（LT）中的半乳糖结合位点，是合理设计潜在抗霍乱药物的一个有吸引力的靶点。在本文中，我们分析了在几个晶体结构中所观察到的该结合位点的分子结构，包括我们在此以2.2埃分辨率报道的LT：半乳糖复合物的晶体结构。游离毒素上的结合表面包含几个紧密结合的水分子以及一个由B亚基的51 - 60位残基组成的相对灵活的环。在受体结合过程中，这个环通过与GM1五糖以及一组稳定毒素：受体复合物的水分子共同形成氢键而变得紧密有序。
