Lehtiö Lari, Grossmann J Günter, Kokona Bashkim, Fairman Robert, Goldman Adrian
Institute of Biotechnology, University of Helsinki, PO Box 65, FIN-00014, Helsinki, Finland.
J Mol Biol. 2006 Mar 17;357(1):221-35. doi: 10.1016/j.jmb.2005.12.049. Epub 2006 Jan 3.
We have solved the crystal structure of a PFL2 from Archaeglobus fulgidus at 2.9 A resolution. Of the three previously solved enzyme structures of glycyl radical enzymes, pyruvate formate lyase (PFL), anaerobic ribonucleotide reductase and glycerol dehydratase (GD), the last one is clearly most similar to PFL2. We observed electron density in the active site of PFL2, which we modelled as glycerol. The orientation of the glycerol is different from that in GD, and changes in the active site indicate that the actual substrate of PFL2 is bigger than a glycerol molecule, but sequence and structural homology suggest that PFL2 may be a dehydratase. Crystal packing, solution X-ray scattering and ultracentrifugation experiments show that PFL2 is tetrameric, unlike other glycyl radical enzymes. A.fulgidus is a hyperthermophile and PFL2 appears to be stabilized by several factors including an increased number of ion pairs, differences in buried charges, a truncated N terminus, anchoring of loops and N terminus via salt-bridges, changes in the oligomeric interface and perhaps also the higher oligomerization state of the protein.
我们已解析了来自嗜热栖热菌的PFL2在2.9埃分辨率下的晶体结构。在之前解析出的三种甘氨酰自由基酶的结构中，即丙酮酸甲酸裂解酶（PFL）、厌氧核糖核苷酸还原酶和甘油脱水酶（GD），最后一种与PFL2明显最为相似。我们在PFL2的活性位点观察到了电子密度，我们将其建模为甘油。甘油的取向与GD中的不同，活性位点的变化表明PFL2的实际底物比甘油分子大，但序列和结构同源性表明PFL2可能是一种脱水酶。晶体堆积、溶液X射线散射和超速离心实验表明，与其他甘氨酰自由基酶不同，PFL2是四聚体。嗜热栖热菌是一种嗜热菌，PFL2似乎通过多种因素得以稳定，包括离子对数量增加、埋藏电荷差异、N端截短、环和N端通过盐桥固定、寡聚界面变化以及蛋白质可能更高的寡聚化状态。
