Department of Biology, University of Rome Tor Vergata, Via Della Ricerca Scientifica, 00133, Rome, Italy.
Amino Acids. 2011 Oct;41(4):945-53. doi: 10.1007/s00726-010-0794-x. Epub 2010 Nov 3.
The N-terminal domain of human topoisomerase IB has been expressed, purified and characterized by spectroscopic techniques. CD spectra as a function of concentration and pH indicate that the domain does not possess any defined secondary structure. The protein is probably in a natively unfolded state since its denaturation curve is indicative of a non-cooperative transition. Evidence of a partially folded structure comes from the fluorescence spectrum of ANS, whose intensity increases in presence of the domain. Indication of a partial structural arrangement of the domain comes also from the endogenous fluorescence of tryptophans that is centred at 350 nm in the native and shifts to 354 nm in the fully denaturated protein. Interestingly despite the poor structural degree, as also confirmed by a predictive approach, the domain efficiently binds DNA, suggesting that the absence of a defined 3D structure has a functional meaning that permits the domain to be available for the interaction with different molecular partners.
人拓扑异构酶 IB 的 N 端结构域已通过光谱技术进行了表达、纯化和特性分析。浓度和 pH 值的 CD 谱表明，该结构域没有任何特定的二级结构。由于其变性曲线表明是不协同的转变，该蛋白可能处于天然无规卷曲状态。部分折叠结构的证据来自于 ANS 的荧光光谱，其强度在该结构域存在时增加。该结构域的部分结构排列的指示还来自于色氨酸的内源性荧光，在天然状态下其中心在 350nm 处，在完全变性的蛋白质中转移到 354nm。有趣的是，尽管结构程度较差，正如预测方法所证实的那样，该结构域能够有效地结合 DNA，这表明缺乏明确的 3D 结构具有功能意义，使该结构域能够与不同的分子伴侣相互作用。
