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MHC-peptide binding is assisted by bound water molecules.
Paula M Petrone1, Angel E Garcia
1Theoretical Biology and Biophysics Group, T-10 MS K710, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
Journal of Molecular Biology
|April 7, 2004
Summary
Water molecules actively mediate interactions between major histocompatibility complex (MHC) and epitopes. These water molecules enhance binding affinity by forming bridges and filling spaces, contributing to the MHC complex
Area of Science:
- Immunology
- Structural Biology
- Computational Chemistry
Background:
- Water molecules are crucial for the high affinity of epitopes to the class I MHC complex.
- Understanding water's role in MHC-peptide interactions is key to explaining binding affinity.
Purpose of the Study:
- To investigate the energy and dynamics of water interactions within the MHC-peptide complex.
- To elucidate the specific roles of interfacial water in MHC-epitope binding.
Main Methods:
- Performed 5ns molecular dynamics simulations of the class I MHC-HLA2 complex with and without an HIV reverse transcriptase epitope.
- Analyzed water penetration at the MHC-peptide interface and identified long-term bound water molecules.
Main Results:
- Identified 14 water molecules bound for over 1ns at the MHC-peptide interface.
- Observed water molecules forming hydrogen bonds and filling spaces, enhancing binding energy.
- Calculated a net gain in free energy from water clusters at the interface, with entropic gain for space-filling water.
Conclusions:
- Interfacial water molecules act as active mediators in MHC-peptide interactions.
- Water's role in binding affinity may explain the MHC complex's interaction with diverse epitope sequences.