Mn^(2+)对apo-CP43结构影响的光谱学研究

Effects of Mn^(2+) on The Structure of apo-CP43 by Spectroscopic Methods

CP43是PSⅡ中的内周天线色素结合蛋白,对PSⅡ的组装、结构稳定、能量传递、电荷分离、光合放氧等功能均起到重要的作用。作者应用内源荧光光谱、同步荧光光谱、傅立叶变换红外光谱(Fourier transform infrared,FTIR)和圆二色谱(circular dichroism,CD)方法检测了Mn2+对纯化的apo-CP43结构的影响。荧光发射和同步荧光光谱表明Mn2+诱导apo-CP43中色氨酸和酪氨酸残基周围疏水性增加,极性降低。Mn2+主要通过静态过程淬灭apo-CP43的荧光,并与apo-CP43形成一个复合体。FTIR和CD光谱显示Mn2+诱导apo-CP43中无规卷曲的含量下降、α-螺旋的含量增加,表明无规卷曲结构向α-螺旋转变,Mn2+与apo-CP43结合形成了一个更为紧密的结构。

CP43 （psbC） is an inner antenna protein of photosystem II which binds chlorophyll a and β-carotene. CP43 plays an important role in maintaining the function, energy transfer, charge separation and photosynthetic oxygen evolution in PSII. When determined the effects of Mn^2＋ on the structure of apo-CP43 by means of spectroscopy, the conclusions could be accepted. The fluorescence emission and the synchronous fluorescence spectra suggested that Mn^2＋ induced the increasing hydrophobicity and the reducing polarity around both of the tryptophan and the tyrosine residues in apo-CP43. Mn^2＋ mainly quenched the fluorescence of apo-CP43 in a static process, with the possible formation of a complex, and the electrostatic force was the main binding force between apo-CP43 and Mn^2＋. The FTIR and CD spectra suggested that Mn2. induced the decreasing content of random coil and increasing content of α-helix in apo-CP43, indicating that random coil transformed to α-helix and Mn^2＋ may bind to the apo-CP43 and promote apo-CP43 to form a more compact structure.