Stenkamp Ronald E
Departments of Biological Structure and Biochemistry, Biomolecular Structure Center, University of Washington, Seattle, WA 98195, USA.
Acta Crystallogr D Biol Crystallogr. 2008 Aug;D64(Pt 8):902-4. doi: 10.1107/S0907444908017162. Epub 2008 Jul 17.
The space-group symmetry of two crystal forms of rhodopsin (PDB codes 1gzm and 2j4y; space group P3(1)) can be re-interpreted as hexagonal (space group P6(4)). Two molecules of the G protein-coupled receptor are present in the asymmetric unit in the trigonal models. However, the noncrystallographic twofold axes parallel to the c axis can be treated as crystallographic symmetry operations in the hexagonal space group. This halves the asymmetric unit and makes all of the protein molecules equivalent in these structures. Corrections for merohedral twinning were also applied in the refinement in the higher symmetry space group for one of the structures (2j4y).
视紫红质两种晶体形式（蛋白质数据银行代码1gzm和2j4y；空间群P3(1)）的空间群对称性可重新解释为六方晶系（空间群P6(4)）。在三角模型的不对称单元中存在两个G蛋白偶联受体分子。然而，平行于c轴的非晶体学二重轴可被视为六方空间群中的晶体学对称操作。这使得不对称单元减半，并使这些结构中的所有蛋白质分子等效。对于其中一个结构（2j4y），在更高对称性空间群的精修中也应用了对映体孪晶校正。
