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Interaction of Anionic Surfactants with Native and Partially Unfolded RNase A: Binding Kinetics, Structural Changes,
Sanjay Kumar1, N Prakash Prabhu1
1Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India.
ACS Omega
|July 7, 2025
Summary
Surfactant alkyl chain length and protein structure influence binding and unfolding. Partially unfolded ribonuclease A (rd-RNase A) shows distinct interactions and unfolding pathways compared to native ribonuclease A (ox-RNase A) due to exposed hydrophobic surfaces.
Area of Science:
- Biochemistry
- Chemical Biology
- Protein Science
Background:
- Protein structure and stability are crucial for biological function.
- Surfactants are widely used to study protein unfolding and interactions.
- The role of alkyl chain length and protein conformation in surfactant binding is not fully understood.
Purpose of the Study:
- To investigate the interactions between different alkyl chain length surfactants (sodium octyl sulfate, decyl sulfate, dodecyl sulfate) and native (ox-RNase A) versus partially unfolded (rd-RNase A) ribonuclease A.
- To elucidate the impact of surfactant concentration (monomeric vs. micellar) on protein structure and stability.
- To compare the unfolding pathways induced by surfactants in different protein conformational states.
Main Methods:
- Surface Plasmon Resonance (SPR) for binding affinity measurements.
- Optical spectroscopy to monitor structural changes.
- Molecular Dynamics (MD) simulations to analyze protein-surfactant interactions at the atomic level.
- Partial reduction of disulfide bonds to generate partially unfolded ribonuclease A.
Main Results:
- Surfactant binding affinity differs between ox-RNase A and rd-RNase A.
- Monomeric surfactants do not significantly alter protein structure.
- Micellar surfactants induce unfolding in ox-RNase A (loss of tertiary interactions, β-sheets, formation of non-native α-helices).
- rd-RNase A initially stabilizes with increased β-sheets but eventually unfolds via non-native α-helices.
- rd-RNase A promotes higher surfactant micelle aggregation numbers.
- Hydrophobic interactions become significant at micellar concentrations, facilitated by exposed surfaces on rd-RNase A.
Conclusions:
- The alkyl chain length of surfactants and the protein's conformational state (native vs. partially unfolded) significantly dictate protein-surfactant interactions and unfolding mechanisms.
- Partially unfolded proteins with exposed hydrophobic surfaces exhibit distinct binding and unfolding pathways compared to their native counterparts.
- These findings contribute to understanding protein behavior in complex biological and chemical environments.
