Biomolecular interactions of lysosomotropic surfactants with cytochrome c and its effect on the protein conformation: A biophysical approach

The molecular interactions between two single-chain lysosomotropic surfactants DMM-11 (2-Dodecanoyloxyethyl)trimethylammonium bromide) and DMPM-11 (2-Dodecanoyloxypropyl)trimethylammonium bromide) with a small heme-protein (cytochrome c (cyt-c)) in Hepes buffer (pH = 7.4) were extensively investigated by surface tension, dynamic light scattering (DLS), circular dichroism (CD) and fluorescence spectroscopy in combination with molecular dynamic simulation techniques. The results demonstrated that surfactants can destroy the hydrophobic cavity of cyt-c, make the α-helical become loose and convert it into the β-sheet structure. The interactions between surfactants and cyt-c are mainly hydrophobic. Molecular modelling approaches were also used to gather a deeper insight on the binding of lysosomotropic surfactants with cyt-c and the in silico results were found to be in good agreement with the experimental ones. This study provides a molecular basis for the applications of protein-surfactant complexes in biological, food, pharmaceutical, industrial and cosmetic systemsPolish-Portugal Executive Program for years 2017–2018 sponsored by the Polish Ministry of Science and Higher Education and by the Portuguese Foundation for Science and Technology (FCT). Additionally, FCT supported the study under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684). T. Janek was supported by the National Science Centre, Poland, projects 2017/26/E/NZ9/00975 and 2018/02/X/NZ6/02201. L. R. Rodrigues acknowledges FCT for the grant SFRH/BSAB/142873/2018. E. J. Gudiña was supported by the grant UMINHO/BPD/39/2015 funded by FCT under the scope of the project UID/BIO/04469/2013