稀土离子(Ho,Er,Yb)与八肋游仆游虫中心蛋白N端半分子作用的光谱研究

Spectral Study on Binding of Lanthanide(Ho,Er,Yb) with N-Terminal Domain of Euplotes Octocarinatus Centrin

在0.01 mol·L-1Hepes,0.15 mol·L-1Na Cl,p H 7.4及室温条件下,采用紫外差光谱和荧光光谱的方法研究了稀土离子Ho(III),Er(III),Yb(III)与八肋游仆虫中心蛋白N端半分子(N-terminal domain of Euplotes octocarinatus centrin,N-Eo Cen)的结合性质。结果表明:稀土离子Ho(III),Er(III),Yb(III)与N-Eo Cen结合导致蛋白质高级结构发生明显变化,疏水区暴露增加。二甲酚橙为竞争配体测得稀土离子Ho(III),Er(III),Yb(III)与N-Eo Cen两个位点的结合能力分别为:lg KI,Ho(III)=5.47±0.37,lg KII,Ho(III)=5.07±0.45;lg KI,Er(III)=5.78±0.42,lg KII,Er(III)=5.36±0.52;lg KI,Yb(III)=5.80±0.65,lg KII,Yb(III)=5.37±0.61。

The binding of Ho（ Ⅲ）, Er（ Ⅲ）, Yb （Ⅲ） with the N-terminal domain of Euplotes octocarinatus cen- trin （N-EoCen） were investigated by fluorescence spectra and difference UV-Vis spectra in 0.01 mol·L-1 Hepes, 0. 15 mol·L-1 NaC1 at pH 7.4 and room temperature. Lanthanide including Ho（Ⅲ）, Er（Ⅲ）, Yb（Ⅲ） binding with N-EoCen resulted in the conformation of N-EoCen changed from closed state to open state and was accompa- nied by enhancement of the exposed hydrophobic surfaces. Using xylenol orange as luminescent and competitive lig- and, the conditional binding constants of site I and Ⅲ on N-EoCen with Ho（ Ⅲ）, Er（Ⅲ） and Yb（Ⅲ） were calcu- lated to be lgKi, Ho（Ⅲ） =5.47±0.37, lgKu, Ho（Ⅲ） =5. 07 ±0. 45 ; lgKi, Er（Ⅲ） =5. 78 ±0. 42, lgKn, Er（Ⅲ） =5. 36 ± 0. 52 ; lgKi, Yb （Ⅲ） = 5. 80 ± 0.65, lgKii＇ Yb（In） = 5.37 ± 0.61, respectively.