Engineering Cytochrome C with Quantum Dots and Ionic Liquids: A Win-Win Strategy for Protein Packaging against Multiple Stresses

Abstract

Enhancing the structural stability and catalytic activity of Cytochorme c (Cyt C) against harsh process conditions would boost its use in biocatalysis. Herein, a new protein engineering strategy with improved efficacy is demonstrated through judicious task-specific functionalization of Cyt C with quantum dots (QDs) and ionic liquids (ILs). Mn2+ doped ZnS QD and ILs ([Cho][Ac]; [Cho][Dhp]) were concomitantly used to decorate Cyt C, which was characterized using various analytical tools. The peroxidase activity at room temperature of engineered Cyt C (Cyt C-QD-IL) increased markedly (1.2 to 3.5-fold) as compared to that for bare Cyt C, Cyt C with QD, and Cyt C with ILs. Further, Cyt C-QD-IL showed better catalytic activity under various stresses such as high temperature (110 °C), presence of a chemical denaturant (6 M GuHCl), high oxidative stress (30 min H2O2), and presence of proteases. Molecular docking results indicate that QD interacted with the active site of Cyt C and IL interacted with side chain amino acids via electrostatic and H-bonding interactions. Such favorable allosteric interactions might be behind the improved activity of Cyt C-QD-IL. The observed catalytic activity is in harmony with the structural stability of the protein as confirmed by UV–vis, ATR-IR, and CD analysis. Thus, the unveiled strategy represents an innovative dimension of protein packaging foreseeing the development of more robust biocatalysts that can be used at high temperatures.