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A model of water structure inside the HLA-A2 peptide binding groove
W S Meng1, H von Grafenstein, I S Haworth
1Department of Pharmaceutical Sciences, University of Southern California, Los Angeles 90033, USA.
Abstract:
Based on molecular dynamics simulations, it is proposed that water within the binding groove of the human MHC class I molecule HLA-A2 plays a role in the formation of its complex with the influenza matrix protein (residues 58-66; GILGFVFTL) peptide. In these simulations, a loosely structured network of water molecules is present in the binding groove between the peptide and the MHC molecule, and may be important in completing the peptide-MHC interface. In two independent 400 ps simulations where groove-based water molecules were included, the peptide remained essentially in the conformation observed in the crystal structure. In contrast, in a 400 ps simulation in which no water molecules were placed between the peptide and the MHC molecule, the crystal structure conformation was rapidly lost. The basis for this behavior appears to be that the groove-based water molecules help to maintain the appropriate orientation of the Arg-97 side chain of HLA-A2 and, in turn, the conformation of the central part of the peptide.
Insights
Water molecules in the binding groove of human MHC class I HLA-A2 are crucial for stabilizing the complex with influenza peptides. Simulations show water maintains peptide conformation, essential for the peptide-MHC interface.
Area of Science:
- Structural biology
- Computational biophysics
- Immunology
Background:
- The human leukocyte antigen (HLA) class I molecule HLA-A2 presents peptide antigens to T cells.
- Understanding the molecular interactions within the peptide-MHC binding groove is key to immunology and drug design.
- The role of water molecules in stabilizing protein-peptide complexes is often overlooked.
Purpose of the Study:
- To investigate the role of water molecules in the binding groove of HLA-A2 during complex formation with an influenza matrix peptide.
- To determine if water influences the stability and conformation of the peptide-MHC complex.
Main Methods:
- Molecular dynamics simulations were employed to model the HLA-A2/influenza peptide complex.
- Simulations were conducted with and without water molecules in the peptide-MHC binding groove.
- Analysis focused on peptide conformation and interactions within the groove.
Main Results:
- A loosely structured water network was observed in the binding groove when water was included.
- Including water molecules maintained the peptide's crystal structure conformation in simulations.
- Excluding water led to a rapid loss of the peptide's native conformation.
Conclusions:
- Water molecules within the HLA-A2 binding groove are essential for stabilizing the peptide-MHC complex.
- These water molecules help maintain the conformation of the influenza peptide by orienting key residues like Arg-97.
- The findings highlight the importance of solvation effects in peptide-MHC interactions.