Effect of Tb(Ⅲ) on the unfolding of ciliate Euplotes octocarinatus centrin induced by guanidine hydrochloride  

作　　者：Enxian Shi Wenlong Zhang Binsheng Yang 

机构地区：[1]Institute of Molecular Science, Shanxi University [2]Department of Pharmacy, Shanxi Medical University

出　　处：《Journal of Rare Earths》2018年第2期203-208,共6页稀土学报（英文版）

基　　金：Project supported by the National Natural Science Foundation of China(21571117);the PhD Programs Foundation of the Ministry of Education of China(20131401110011)

摘　　要：To understand the unfolding of ciliate Euplotes octocarinatus centrin（EoCen）, the glycine positioned at 115, the sixth residue of the loop of the protein＇s third EF-hand, was mutated into tryptophan（Trp）.Intrinsic fluorescence and Tb（Ⅲ） binding properties of wild type EoCen and G115W mutant were monitored by fluorescence spectra in 10 mmol/L Hepes. The emission maximum of EoCen was 306 nm and mutation had no impact on the Tb（Ⅲ） binding properties. The properties of G115W were investigated by fluorescence, far-UV circular dichroism（CD） spectra and fluorescence decays in the absence or in the presence of 6 mol/L guanidine hydrochloride（GdnHCl）. For the increase in polarity of microenvironment around Trp residue, the emission maximum of apoG115 W at 343 nm is shifted to 359 nm in 6 mol/L GdnHCI. Also the secondary structure is lost nearly and fluorescence lifetime decreases in 6 mol/L GdnHCI. The unfolding of G115W induced by GdnHCI was assessed by using the model of structural element The unfolding of proteins is a sequential reaction, namely two-transition. three-state process. The first transition belongs to the unfolding of the C-terminal domain, and the second transition is assigned to the unfolding of the N-terminal domain. The ⊿〈△G_（total）~0（H_2O）〉 was used to determine the effect of Tb（Ⅲ） on the stability of apoprotein. The 〈△G_（total）~0（H_2 O）〉for Tb_2-G115 W has a less increase of0.68 kJ/mol compared with apoG115W, proving Tb（Ⅲ） situated at C-terminal has negligible impact on the stability of protein. Whereas the 〈△G_（total）~0（H_2 O）〉 for Tb_4-G115W has a rise of 1.29 kJ/mol compared with Tb_2-G115W, manifesting Tb（Ⅲ） lcocated at low affinity sites has considerable influence on protein stability. mainly stabilizing the N-terminal domain.To understand the unfolding of ciliate Euplotes octocarinatus centrin（EoCen）, the glycine positioned at 115, the sixth residue of the loop of the protein＇s third EF-hand, was mutated into tryptophan（Trp）.Intrinsic fluorescence and Tb（Ⅲ） binding properties of wild type EoCen and G115W mutant were monitored by fluorescence spectra in 10 mmol/L Hepes. The emission maximum of EoCen was 306 nm and mutation had no impact on the Tb（Ⅲ） binding properties. The properties of G115W were investigated by fluorescence, far-UV circular dichroism（CD） spectra and fluorescence decays in the absence or in the presence of 6 mol/L guanidine hydrochloride（GdnHCl）. For the increase in polarity of microenvironment around Trp residue, the emission maximum of apoG115 W at 343 nm is shifted to 359 nm in 6 mol/L GdnHCI. Also the secondary structure is lost nearly and fluorescence lifetime decreases in 6 mol/L GdnHCI. The unfolding of G115W induced by GdnHCI was assessed by using the model of structural element The unfolding of proteins is a sequential reaction, namely two-transition. three-state process. The first transition belongs to the unfolding of the C-terminal domain, and the second transition is assigned to the unfolding of the N-terminal domain. The ⊿〈△G_（total）~0（H_2O）〉 was used to determine the effect of Tb（Ⅲ） on the stability of apoprotein. The 〈△G_（total）~0（H_2 O）〉for Tb_2-G115 W has a less increase of0.68 kJ/mol compared with apoG115W, proving Tb（Ⅲ） situated at C-terminal has negligible impact on the stability of protein. Whereas the 〈△G_（total）~0（H_2 O）〉 for Tb_4-G115W has a rise of 1.29 kJ/mol compared with Tb_2-G115W, manifesting Tb（Ⅲ） lcocated at low affinity sites has considerable influence on protein stability. mainly stabilizing the N-terminal domain.

关 键 词：Euplotes octocarinatus centrin Tb（Ⅲ） Unfolding Structure element Stability Rare earths 

分 类 号：Q51[生物学—生物化学]