Unfolding pathway of cytochrome c oxidase induced by ionic surfactants: Circular dichroism and picosecond time-resolved fluorescence studies

摘要: The unfolding of the membrane protein, cytochromec oxidase (CcO) induced by ionic surfactants have been studied using circular dichroism, optical absorbance and time resolved tryptophan fluorescence spectroscopic methods. Ionic surfactant cetyltrimethyl ammonium bromide (CTAB) was found to cause denaturation this protein leading release both, hemea residues from CcO indicated both CD titration. Upon dissociation hemes matrix; intensity increased drastically lifetimes became much longer compared short observed in native protein. shortest lifetime 70 ps due strong quenching (energy transfer) heme groups, ∼10-fold CTAB-unfolded indicating complete removal groups matrix. Remarkable differences were between mode actions commonly used denaturant guanidine hydrochloride. Improved data analysis maximum entropy method showed that distribution pattern two cases very different. hydrochloride unfolded shorter more widely distributed are probably not separated away matrix state is highly heterogeneous. Our results further lauryl maltoside inhibits initial step possibly involves quantitative replacement at surface enzyme.