Buchko Garry W
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
Protein Pept Lett. 2010 Jul;17(7):831-5. doi: 10.2174/092986610791306689.
The crystal structure for the Deinococcus radiodurans Nudix protein DR_0079 was recently determined in the metal-free form at 1.9 A resolution (2O5F). The protein adopts the fundamental fold common to the Nudix family of proteins, a large mixed b-sheet sandwiched between the a-helix of the "Nudix box" and a second a-helix. The protein's physical properties were further characterized by circular dichroism (CD) spectroscopy. A CD thermal melt at 220 nm identifies an inflection point at approximately 52 degrees C. However, unlike typical CD thermal melts, the negative ellipticity at 220 nm becomes more negative upon passing through the inflection point. Both NMR spectroscopy and size exclusion chromatography indicate that heating effects the irreversible formation of a large molecular weight complex. After cooling, the negative ellipiticity at 220 nm increases further, and overall, the CD spectrum at 25 degrees C suggests that heat-treated DR_0079 has more a-helical and b-sheet structure than non-heat treated DR_0079.
最近，嗜放射栖热菌（Deinococcus radiodurans）Nudix蛋白DR_0079的晶体结构以无金属形式在1.9埃分辨率下得以确定（2O5F）。该蛋白呈现出Nudix蛋白家族共有的基本折叠结构，即一个大的混合β折叠夹在“Nudix框”的α螺旋和第二个α螺旋之间。通过圆二色性（CD）光谱对该蛋白的物理性质进行了进一步表征。在220纳米处的CD热变性曲线确定了一个约52摄氏度的拐点。然而，与典型的CD热变性曲线不同，在220纳米处的负椭圆率在经过拐点时变得更负。核磁共振光谱和尺寸排阻色谱均表明，加热会导致形成一种不可逆的大分子量复合物。冷却后，220纳米处的负椭圆率进一步增加，总体而言，25摄氏度下的CD光谱表明，经热处理的DR_0079比未经热处理的DR_0079具有更多的α螺旋和β折叠结构。
