Xu Yibin, Carr Paul D, Clancy Paula, Garcia-Dominguez Mario, Forchhammer Karl, Florencio Francisco, Vasudevan Subhash G, Tandeau de Marsac Nicole, Ollis David L
Department of Biochemistry and Molecular Biology, James Cook University, Townsville, Queensland 4811, Australia.
Acta Crystallogr D Biol Crystallogr. 2003 Dec;59(Pt 12):2183-90. doi: 10.1107/s0907444903019589. Epub 2003 Nov 27.
The PII proteins from the cyanobacteria Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803 have been crystallized and high-resolution structures have been obtained using X-ray crystallography. The core of these new structures is similar to that of the PII proteins from Escherichia coli, although the structures of the T- and C-loops differ. The T-loop of the Synechococcus protein is ordered, but appears to be stabilized by crystal contacts. The same loop in the Synechocystis protein is disordered. The C-terminus of the Synechocystis protein is stabilized by hydrogen bonding to the same region of a crystallographically related molecule. The same terminus in the Synechococcus protein is stabilized by coordination with a metal ion. These observations are consistent with the idea that both the T-loop and the C-terminus of PII proteins are flexible in solution and that this flexibility may be important for receptor recognition. Sequence comparisons are used to identify regions of the sequence unique to the cyanobacteria.
来自蓝藻聚球藻属PCC 7942和集胞藻属PCC 6803的PII蛋白已被结晶，并通过X射线晶体学获得了高分辨率结构。这些新结构的核心与来自大肠杆菌的PII蛋白相似，尽管T环和C环的结构有所不同。聚球藻蛋白的T环是有序的，但似乎通过晶体接触得以稳定。集胞藻蛋白中的同一环是无序的。集胞藻蛋白的C末端通过与晶体学相关分子的同一区域形成氢键而得以稳定。聚球藻蛋白中的同一末端通过与金属离子配位而得以稳定。这些观察结果与以下观点一致，即PII蛋白的T环和C末端在溶液中都是灵活的，并且这种灵活性可能对受体识别很重要。序列比较用于识别蓝藻特有的序列区域。
