Department of Food and Cosmetic Science, Faculty of Bioindustry, Tokyo University of Agriculture, 196 Yasaka, Abashiri, Hokkaido 099-2493, Japan.
Biochem Biophys Res Commun. 2013 Aug 30;438(3):483-7. doi: 10.1016/j.bbrc.2013.07.112. Epub 2013 Aug 2.
Large-sized botulinum toxin complex (L-TC) is formed by conjugation of neurotoxin, nontoxic nonhemagglutinin and hemagglutinin (HA) complex. The HA complex is formed by association of three HA-70 molecules and three HA-33/HA-17 trimers, comprised of a single HA-17 and two HA-33 proteins. The HA-33/HA-17 trimer isolated from serotype D L-TC has the ability to bind to and penetrate through the intestinal epithelial cell monolayer in a sialic acid-dependent manner, and thus it plays an important role in toxin delivery through the intestinal cell wall. In this study, we determined the solution structure of the HA-33/HA-17 trimer by using small-angle X-ray scattering (SAXS). The SAXS image of HA-33/HA-17 exhibited broadly similar appearance to the crystal image of the complex. On the other hand, in the presence of N-acetylneuraminic acid, glucose and galactose, the solution structure of the HA-33/HA-17 trimer was drastically altered compared to the structure in the absence of the sugars. Sugar-induced structural change of the HA-33/HA-17 trimer may contribute to cell binding and subsequent transport across the intestinal cell layer.
大尺寸肉毒毒素复合物（L-TC）是由神经毒素、非毒性非血凝素和血凝素（HA）复合物通过共轭形成的。HA 复合物是由三个 HA-70 分子和三个 HA-33/HA-17 三聚体组成的，每个三聚体由一个 HA-17 和两个 HA-33 蛋白组成。从血清型 D L-TC 中分离出的 HA-33/HA-17 三聚体具有以唾液酸依赖性方式结合并穿透肠上皮细胞单层的能力，因此它在通过肠细胞壁输送毒素方面发挥着重要作用。在这项研究中，我们使用小角度 X 射线散射（SAXS）来确定 HA-33/HA-17 三聚体的溶液结构。HA-33/HA-17 的 SAXS 图像与该复合物的晶体图像具有广泛相似的外观。另一方面，在存在 N-乙酰神经氨酸、葡萄糖和半乳糖的情况下，与无糖时的结构相比，HA-33/HA-17 三聚体的溶液结构发生了剧烈变化。HA-33/HA-17 三聚体的糖诱导结构变化可能有助于细胞结合和随后穿过肠细胞层的运输。
