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Computational Biophysics of Membrane Proteins

Computational Biophysics of Membrane Proteins

Carmen Domene

(2016)

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Book Details

Abstract

Exploring current themes in modern computational and membrane protein biophysics, this book presents a comprehensive account of the fundamental principles underlying different methods and techniques used to describe the intriguing mechanisms by which membrane proteins function. The book discusses the experimental approaches employed to study these proteins, with chapters reviewing recent crucial structural advances that have allowed computational biophysicists to discern how these molecular machines work. The book then explores what computational methods are available to researchers and what these have taught us about three key families of membrane proteins: ion channels, transporters and receptors. The book is ideal for researchers in computational chemistry and computational biophysics.
Carmen Domene is a Reader in Computational Chemistry at King’s College London, UK. Her research group applies principles from quantum mechanics and statistical thermodynamics to model biomolecular phenomena with computer simulations.

Table of Contents

Section Title Page Action Price
Cover Cover
Contents v
Chapter 1 Introduction to the Structural Biology of Membrane Proteins 1
1.1 Introduction 1
1.2 Membrane Features 2
1.3 Lipid Polymorphism 5
1.4 Classes of Membrane Proteins 7
1.4.1 α-Helical Bundles\r 7
1.4.2 β-Barrels\r 8
1.5 Functions of Membrane Proteins 9
1.5.1 Channels 10
1.5.2 Transporters 11
1.5.3 Enzymes 14
1.5.4 Receptors 14
1.6 Membrane Protein Complexes 15
1.7 Conclusions 17
References 17
Chapter 2 Molecular Dynamics Simulations: Principles and Applications for the Study of Membrane Proteins 19
2.1 Introduction 19
2.2 Classical Molecular Dynamics 20
2.2.1 Additive Force Fields 22
2.2.2 Polarisable Force Fields 24
2.2.3 Practical and Technical Considerations 25
2.2.4 Applications 29
2.3 Coarse-grained Molecular Dynamics Simulations 30
2.4 Ab initio Molecular Dynamics 33
2.5 Enhanced Sampling Techniques and Free Energy Methods 34
2.6 Conclusions 40
References 40
Chapter 3 Free Energy Calculations for Understanding Membrane Receptors 59
3.1 Introduction 59
3.2 The Basics of Free Energy Calculations 60
3.2.1 The Parametric Formulation of Free Energy Calculations 60
3.2.2 Ergodicity, Variance Reduction Strategies, and the Transition Coordinate 63
3.3 Free Energy Perturbation Methods 65
3.3.1 Theoretical Background 65
3.3.2 Alchemical Transformations 70
3.4 Probability Distribution Methods 73
3.5 Thermodynamic Integration 75
3.5.1 Theoretical Background 75
3.5.2 Adaptive Biasing Force Method 78
3.6 Replica Exchange for Enhanced Sampling in Configurational Space 80
3.7 Applications of Free Energy Calculations: Case Studies 81
3.7.1 Binding of Anesthetic Ligands to Receptors 82
3.7.2 Free Energies of Ions across Channels 84
3.7.3 Conformational Transitions in Receptors 86
3.8 Non-equilibrium Properties from Free Energy Calculations 88
3.8.1 Theoretical Background 90
3.8.2 Example - the Leucine-Serine Channel 93
3.9 Summary and Conclusions 96
References 98
Chapter 4 Non-atomistic Simulations of Ion Channels 107
4.1 Introduction 107
4.2 Methods Based on Continuum Distributions of Ions 111
4.2.1 Poisson-Boltzmann 112
4.2.2 Poisson-Nernst-Planck 117
4.2.3 Improvements of Classical Continuum Theories of Electrolytes 119
4.3 Particle-based Methods 122
4.3.1 Brownian Dynamics 124
4.3.2 Monte Carlo 127
4.4 Methods to Include Atomic Detail in Non-atomistic Models 128
4.4.1 Atomic Detail in Brownian Dynamics 129
4.4.2 Atomic Detail in Continuum Models 132
4.5 Concluding Remarks 133
References 133
Chapter 5 Experimental and Computational Approaches to Study Membranes and Lipid–Protein Interactions 137
5.1 Introduction 137
5.1.1 Membrane Components 138
5.2 Role of Membrane Lipids in Membrane Protein Organization and Function 139
5.3 Mechanisms for Lipid Regulation of Membrane Proteins 140
5.3.1 Specific Membrane Effects 140
5.3.2 Non-specific Membrane Effects 142
5.4 Range of Time Scales Exhibited by Membranes 142
5.5 Lipid-Protein Interactions: Insights from Experimental Approaches 144
5.5.1 Determining Near-neighbor Relationships in Membranes: Interaction of Melittin with Membrane Cholesterol utilizing FRET 144
5.5.2 Interaction of the Actin Cytoskeleton with GPCRs: Application of FRAP 147
5.6 Computational Approaches to Study Membrane Organization and Lipid-Protein Interactions 149
5.6.1 Simulating Single Component and Multi-component Bilayers 151
5.6.2 Atomistic Simulations Elucidating Lipid-Protein Interactions 151
5.6.3 Coarse-grain Methods to Analyze Membrane Protein Interactions 153
5.6.4 Enhanced Sampling Methods 154
5.7 Future Perspectives: The Road Ahead 155
Acknowledgments 155
References 155
Chapter 6 Computer Simulation of Ion Channels 161
6.1 Introduction to Ion Channels 161
6.2 Questions that can be Addressed and Associated Timescales 165
6.3 Ion Permeation 169
6.4 Ion Selectivity 174
6.4.1 Na+/Ca2+ Selection 174
6.4.2 Na+/K+ Selection 177
6.5 Channel Gating 181
6.6 Interactions of Channels with Drugs and Toxins 184
6.6.1 Toxin-Channel Interactions 184
6.6.2 Channel Blockage by Small Molecules 187
6.7 Conclusions 189
Acknowledgments 190
References 190
Chapter 7 Computational Characterization of Molecular Mechanisms of Membrane Transporter Function 197
7.1 Membrane Transport – A Fundamental Biological Process 197
7.2 Substrate Binding and Unbinding 200
7.2.1 Spontaneous Binding Simulations Revealing a Binding Mechanism and Site 201
7.2.2 Proposing Substrate Binding Sites through Molecular Docking 202
7.2.3 Unraveling Substrate Release Pathways 204
7.3 Capturing Localized Transporter Motions with Equilibrium Molecular Dynamics 205
7.3.1 Substrate-induced Structural Changes of an Antiporter 206
7.3.2 Gating Elements in a Neurotransmitter Transporter 206
7.4 Computational Description of Global Structural Transitions in Membrane Transporters 209
7.4.1 Nonequilibrium Simulation of Structural Changes 210
7.4.2 Application to an ABC Transporter 212
7.5 Water within Transporters 215
7.5.1 Water Leaks in Transporters 216
7.5.2 Water in Proton Pathways 216
7.6 The Lipid Frontier 219
7.6.1 Why Now? Initial Barriers to Simulating Lipid-Protein Interactions 219
7.6.2 Computational Probes of Lipid-Protein Interactions 220
7.7 Concluding Remarks 221
Acknowledgments 222
References 223
Chapter 8 Computational Studies of Receptors 237
8.1 Introduction 237
8.2 Network Models Can Provide Insight into Large-scale Conformational Changes 239
8.3 Network Models to Examine Gating 241
8.4 Network Models to Compare Dynamics 242
8.5 Network Models to Suggest Novel Mechanisms for Modulation 244
8.6 Molecular Dynamics to Aid Crystallographic Interpretation 245
8.7 Molecular Dynamics to Move between States 247
8.8 Molecular Dynamics to Refine Working Models 249
8.9 Molecular Dynamics to Explain the Effects of Ions and Water 251
8.10 Molecular Dynamics to Quantify Free Energy Requirements 253
8.11 Conclusions 255
References 255
Subject Index 259