Differential exposure of aromatic amino acids in the red-light-absorbing and far-red-light-absorbing forms of 124-kDa oat phytochrome.
Differential exposure of aromatic amino acids in the red-light-absorbing and far-red-light-absorbing forms of 124-kDa oat phytochrome.
复制标题
124-kDa 燕麦光敏色素的红光吸收和远红光吸收形式中芳香族氨基酸的暴露差异。
DOI：
10.1111/j.1432-1033.1989.tb15071.x
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Rüdiger,W
中科院分区：
文献类型：
--
作者：
Singh,BR;Song,PS;Eilfeld,P;Rüdiger,W
用紫外可见吸收光谱和紫外圆二色光谱研究了光敏色素的芳香族氨基酸残基和其他疏水基团的表面形貌。使用了三种不同类型的环糊精(α，β和γ)，它们具有不同的疏水空腔大小。络合作用使紫外区(222 Nm)、中紫外区(280 nm和300 nm)、近紫外区(365 Nm)和可见光区(670 Nm)光敏色素的红光吸收(PR)和远红光吸收(PFR)的圆二色信号发生了显著变化。α-和β-环糊精对Pr中紫外光CD信号的抑制效果明显优于PfR，表明芳香族氨基酸残基的差异包合作用。γ-环糊精没有表现出明显的分化。对光敏色素-环糊精络合物的二级结构分析表明，Pr和PfR两种形式的α-螺旋含量都显著增加。PfR形式(17-25%)的增加大约是Pr形式(8-9%)的两倍，这表明络合对光敏色素蛋白构象的不同影响。虽然环糊精的络合作用不影响光敏色素的光静态平衡，但Pr、→、PfR光转化速率显著提高。但对PfR、→、Pr光还原无明显影响。结果表明，由于两种形式的芳香族氨基酸的可及性不同，环糊精与光敏色素的Pr和Pfr形式的络合作用不同。对280 nm附近的吸收差光谱和圆二色光谱的详细分析也揭示了芳香族氨基酸暴露的差异。
The surface topography of aromatic amino acid residues and/or other hydrophobic groups of phytochrome has been investigated by ultraviolet absorption spectra and ultraviolet circular dichorism using phytochromecyclodextrin inclusion complexation. Three different types of cyclodextrins (α, β and γ) with varying hydrophobic cavity sizes, were used. Complexation resulted in significant changes in the circular dichroic signals of both the red‐light‐absorbing (Pr) and far‐red‐light‐absorbing (Pfr) forms of phytochrome in the ultraviolet region at 222 nm, mid‐ultraviolet at 280 nm and 300 nm and in the near‐ultraviolet and visible regions at 365 nm and 670 nm, respectively. α‐ and β‐Cyclodextrins were markedly (1.7–4.5‐fold) more effective in reducing the midultraviolet CD signal of Pr than that of Pfr, indicating a differential inclusion of the aromatic amino acid residues. γ‐Cyclodextrin did not exhibit any significant differentiation. Secondary structure analysis of the phytochrome‐cyclodextrin complexes revealed a considerable increase in the α‐helical contents of both Pr and Pfr forms. The increase in the Pfr form (17–25%) was about twice that in the Pr form (8–9%), indicating a differential effect of complexation on the conformation of the phytochrome protein. Although the photostationary‐state equilibrium of the phytochrome was not affected by the cyclodextrin complexation, the Pr → Pfr phototransformation rate was significantly increased. However, the Pfr → Pr photoreversion was not affected significantly. The results suggest a differential complexation of cyclodextrins with the Pr and Pfr forms of phytochrome as a result of a difference in accessibility of aromatic amino acids in the two forms. A detailed analysis of absorption difference spectra and circular dichroic spectra around 280 nm also revealed evidence for a difference in the exposure of aromatic amino acids.