Vall-Sagarra Alicia, McMicken Brady, Nonell Santi, Brancaleon Lorenzo
Institut Quimic de Sarria, Universitat Ramon Llull, Via Augusta 390, 08017, Barcelona, Spain.
Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX, USA.
Chemphyschem. 2016 Oct 18;17(20):3269-3282. doi: 10.1002/cphc.201600629. Epub 2016 Aug 30.
The formation and the effects of laser irradiation of the complex formed by protoporphyrin IX (PPIX) and tubulin was investigated. We have used tubulin as a model protein to investigate whether docked photoactive ligands can affect the structure and function of polypeptides upon exposure to visible light. We observed that laser irradiation in the Soret band prompts bleaching of the PPIX, which is accompanied by a sharp decrease in the intensity and average fluorescence lifetime of the protein (dominated by the four tryptophan residues of the tubulin monomer). The kinetics indicate non-trivial effects and suggest that the photosensitization of the PPIX bound to tubulin prompts structural alterations of the protein. These modifications were also observed through changes in the energy transfer between Trp residues and PPIX. The results suggest that laser irradiation produces localized partial unfolding of tubulin and that the changes prompt modification of the formation of microtubules in vitro. Measurements of singlet oxygen formation were inconclusive in determining whether the changes are prompted by reactive oxygen species or other excited state mechanisms.
研究了原卟啉 IX（PPIX）与微管蛋白形成的复合物的激光照射形成及其效应。我们使用微管蛋白作为模型蛋白，以研究对接的光活性配体在可见光照射下是否会影响多肽的结构和功能。我们观察到，在索雷特带的激光照射会促使PPIX漂白，同时伴随着蛋白质强度和平均荧光寿命的急剧下降（主要由微管蛋白单体的四个色氨酸残基决定）。动力学表明存在非平凡效应，并表明与微管蛋白结合的PPIX的光致敏作用促使蛋白质发生结构改变。通过色氨酸残基与PPIX之间能量转移的变化也观察到了这些修饰。结果表明，激光照射会使微管蛋白发生局部部分解折叠，并且这些变化会促使体外微管形成的改变。单线态氧形成的测量结果在确定这些变化是由活性氧还是其他激发态机制引起时尚无定论。
