Abstract

In this work, results of studies on the interactions of CopC and its mutants with the cationic surfactant Cetyltrimethyl Ammonium Bromide (CTAB) monitored by fluorescence spectroscopy, far- UV circular dichroism (CD) and fluorescence lifetime have been presented and discussed. The interaction of CTAB with CopC leads to stabilize a second intermediate, which is considered that the structure of C-terminal was unfolded completely and the structure of the N-terminal was partially unfolded. Notably, GdnHCl leads to refolding of the second intermediate and form the first intermediate, which has also been found on unfolding of CopC by sodium dodecyl sulfate (SDS). The refolding of a protein by GdnHCl in the presence of CTAB was reported. The results suggested that the formation of micelle-like aggregates interaction with the protein results in formation of intermediates of apoCopC and the effect of GdnHCl on micelle-like aggregates result in the folding of the second intermediate.

Keywords: Chemical denaturant, CopC, intermediate, surfactant, unfolding.