Soisson S M, MacDougall-Shackleton B, Schleif R, Wolberger C
Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Science. 1997 Apr 18;276(5311):421-5. doi: 10.1126/science.276.5311.421.
The crystal structure of the arabinose-binding and dimerization domain of the Escherchia coli gene regulatory protein AraC was determined in the presence and absence of L-arabinose. The 1.5 angstrom structure of the arabinose-bound molecule shows that the protein adopts an unusual fold, binding sugar within a beta barrel and completely burying the arabinose with the amino-terminal arm of the protein. Dimer contacts in the presence of arabinose are mediated by an antiparallel coiled-coil. In the 2.8 angstrom structure of the uncomplexed protein, the amino-terminal arm is disordered, uncovering the sugar-binding pocket and allowing it to serve as an oligomerization interface. The ligand-gated oligomerization as seen in AraC provides the basis of a plausible mechanism for modulating the protein's DNA-looping properties.
在有和没有L-阿拉伯糖存在的情况下，测定了大肠杆菌基因调节蛋白AraC的阿拉伯糖结合及二聚化结构域的晶体结构。与阿拉伯糖结合的分子的1.5埃结构表明，该蛋白质呈现出一种不寻常的折叠方式，在一个β桶内结合糖类，并通过蛋白质的氨基末端臂将阿拉伯糖完全包埋。在有阿拉伯糖存在时，二聚体接触由一个反平行卷曲螺旋介导。在未结合配体的蛋白质的2.8埃结构中，氨基末端臂无序，露出糖结合口袋，并使其能够作为寡聚化界面。如在AraC中所见的配体门控寡聚化提供了一种合理机制的基础，用于调节该蛋白质的DNA环化特性。
