van Rooyen Jason, Belrhali Hassan, Abratt Valarie, Sewell B Trevor
Electron Microscope Unit, Department of Molecular and Cell Biology, University of Cape Town, South Africa.
Acta Crystallogr Sect F Struct Biol Cryst Commun. 2011 Mar 1;67(Pt 3):358-63. doi: 10.1107/S1744309110053893. Epub 2011 Feb 25.
This work details the intentional modifications that led to the first structure of a type III glutamine synthetase enzyme (GSIII). This approach followed the serendipitous discovery of digestion caused by an extracellular protease from a contaminating bacterium, Pseudomonas fluorescens. The protease only cleaves the GSIII protein at a single site, leaving the oligomer intact but allowing the protein to crystallize in a different space group. This transition from space group P1 to space group C222(1) is accompanied by improved growth characteristics, more reproducible diffraction and enhanced mechanical stability. The crystallographic analyses presented here provide the structural basis of the altered molecular packing in the full-length and digested crystal forms and suggest modifications for future structural studies.
这项工作详细介绍了导致III型谷氨酰胺合成酶（GSIII）首个结构的有意修饰。这种方法是在偶然发现由污染细菌荧光假单胞菌的细胞外蛋白酶引起的消化作用之后采用的。该蛋白酶仅在单个位点切割GSIII蛋白，使寡聚体保持完整，但允许蛋白质在不同的空间群中结晶。从空间群P1到空间群C222(1)的这种转变伴随着改善的生长特性、更可重复的衍射和增强的机械稳定性。本文给出的晶体学分析提供了全长和消化后晶体形式中分子堆积改变的结构基础，并为未来的结构研究提出了修饰建议。
