McMicken Brady, Thomas Robert J, Brancaleon Lorenzo
The University of Texas at San Antonio, Department of Physics and Astronomy, One UTSA Circle, San Antonio, Texas, 78249 USA; Optical Radiation Bioeffects Branch, Bioeffects Division, Air Force Research Laboratory, Fort Sam Houston, Texas 78234, USA.
J Biophotonics. 2014 Nov;7(11-12):874-88. doi: 10.1002/jbio.201300066. Epub 2013 Jul 29.
The irradiation of the complex formed by meso-tetrakis (sulfonatophenyl) porphyrin (TSPP) and tubulin was investigated as well as its effects on the structure and function of the protein. We have used tubulin as a model target to investigate whether photoactive ligands docked to the protein can affect the structure and function of the protein upon exposure to visible light. We observed that laser irradiation prompts bleaching of the porphyrin which is accompanied by a sharp decrease (∼2 ns) in the average fluorescence lifetime of the protein and a change in the dichroic spectrum consistent with a decrease of helical structure. The result indicated the photoinduced partial unfolding of tubulin. We also observed that such partial conformational change inhibits the formation of microtubules in vitro. We investigated whether photosensitization of reactive oxygen species was responsible for these effects. Even upon removal of O2 the protein still undergoes conformational changes indicating that irradiation of the bound porphyrin does not require the presence of O2 to prompt conformational and functional effects opening the possibility that other mechanisms (e.g., charge transfer) are responsible for the photoinduced mechanism.
研究了中位-四（磺化苯基）卟啉（TSPP）与微管蛋白形成的复合物的辐照情况及其对该蛋白质结构和功能的影响。我们以微管蛋白为模型靶点，研究与蛋白质结合的光活性配体在可见光照射下是否会影响蛋白质的结构和功能。我们观察到激光辐照促使卟啉漂白，同时伴随着蛋白质平均荧光寿命急剧下降（约2纳秒）以及二向色光谱变化，这与螺旋结构减少一致。结果表明微管蛋白发生了光诱导的部分解折叠。我们还观察到这种部分构象变化在体外会抑制微管的形成。我们研究了活性氧的光致敏作用是否是这些效应的原因。即使去除O₂，蛋白质仍会发生构象变化，这表明结合的卟啉的辐照不需要O₂的存在来引发构象和功能效应，这意味着其他机制（如电荷转移）可能是光诱导机制的原因。
