Biomembrane Transport (eBook)

Front Cover 1
Biomembrane Transport 4
Copyright Page 5
Contents 8
Foreword 12
Preface 14
Chapter 1. Importance of Biomembrane Transport 16
I. Introduction 16
II. Solute and Solvent Fluxes Are Determined by Barriers and Propelling Forces 18
III. Biomembrane Transport in Context 22
IV. Summary 25
Chapter 2. Biomembrane Composition, Structure, and Turnover 28
I. Introduction 28
II. Is the Fluid Mosaic Model of Membrane Structure Still Adequate? 28
III. Some Components of the Biomembrane Can Be Reconstituted 44
IV. How Are Biomembrane Composition and Structure Regulated? 45
V. Summary 53
Chapter 3. Thermodynamics and Transport 54
I. Introduction 54
II. Similar Mathematical Expressions Serve for the Free Energy Change in a Chemical Reaction and in the Migration of a Solute or Solvent 54
III. Changes in Enthalpy and Entropy May Contribute Differently to the Free Energy Changes Associated with a Biochemical Reaction and Migration of a Solute 58
IV. The Total Chemical Potential Change for a Transport Process Also May Have an Electrical Component 59
V. The Gibbs–Donnan Effect Also Generates Osmotic Pressure 62
VI. Chemical Reactions Drive Primary Active Transport 64
VII. Reversal of Transport May Drive Chemical Reactions 70
VIII. How Do Fluctuations in the Local Hydrogen Ion Potential Facilitate Formation of Phosphoric Acid Anhydride Bonds by the Mitochondrial FoFIATP Synthase? 71
IX. Conversion of Solute Total Chemical Potential Gradients to Gradients of Other Solutes during Co- and Countertransport 72
X. Dissipation of Solute Gradients through Mediated Transport Processes May Also Perform Work 76
XI. Application of Thermodynamic Principles to the Solution of Practical Transport Problems 78
XII. Summary 78
Chapter 4. Transport Kinetics 80
I. Introduction 80
II. Kinetics of Diffusion 81
III. How Do Measurements of both the Diffusional and the Osmotic Permeability Coefficient for Water Inform Us about the Mechanism of Water Transport across a Plasma Membrane? 85
IV. Do Lipophilic Substances Migrate across Biomembrane Phospholipid Bilayers by Simple Diffusion? 88
V. Lipid-Soluble Substances Are Used to Attempt to Measure the Width of Unstirred Water Layers on Either Side of Biomembranes 89
VI. Do Such Determinations of the Apparent Widths of Unstirred Water Layers Reflect the Intended Physical Phenomenon or Our Ignorance of How Lipid-Soluble Substances Cross Biomembranes? 91
VII. Protein versus Lipid-Mediated Mechanisms of Fatty Acid Migration across Biomembranes 94
VIII. Protein-Mediated Biomembrane Transport Is Probably Always Substrate Saturable 96
IX. Kinetics of Saturable Transport 98
X. Identification and Minimization or Deduction of Processes That May Obscure a Transport Process of Interest 113
XI. Kinetic Differences among Substrate-Saturable Transport Processes That Form, Propagate, or Dissipate Solute Gradients 131
XII. Summary 139
Appendix 141
Chapter 5. Structure and Function of Transport Proteins That Form Solute Gradients 148
I. Introduction 148
II. P-Type ATPases 150
III. FoFI–ATP Synthases (F-Type ATPases) 167
IV. Summary 181
Chapter 6. Transport Proteins That Propagate Solute Gradients 184
I. Introduction to Symporters and Antiporters 184
II. Both Erythroid and Nonerythroid Tissues Express Anion Exchangers 185
III. ASC and Excitatory (Anionic) Amino Acid Transporters Comprise One of Two Known Families of Mammalian Na*/Amino Acid Symporters 223
IV. Both AE and EAAT/ASC Proteins Have Additional Functions 248
V. Summary 252
Chapter 7. Channel Proteins Usually Dissipate Solute Gradients 254
I. Introduction 254
II. Structure, Function, and Evolution of Channel Proteins 255
III. Kinetics of Transport via K + and Other Channels 269
IV. Summary 277
Chapter 8. A Proposed System for the Classification of Transmembrane Transport Proteins in Living Organisms 280
I. Introduction 280
II. Work of the Enzyme Commission as a Basis for the Systematic Classification of Transport Proteins 280
III. Phylogeny as a Basis for Protein Classification: Criteria for Family Assignment 281
IV. Proposed Transport Protein Classification System 282
V. Representative Examples of Classified Families 287
VI. Cross-Classification of Transport Proteins 287
VII. The Two Largest Superfamilies of Transporters: The MF and ABC Superfamilies 290
VIII. Macromolecular Transport Proteins in Bacteria 290
IX. Conclusions and Perspectives 291
Chapter 9. Regulation of Plasma Membrane Transport 292
I. Introduction 292
II. Regulation of Transport by Changes in Driving Force: The Role of Plasma Membrane Potential 292
III. Regulation of the Activity of Existing Transporters through Modifications of Transporter Molecules 293
IV. Regulation of Transport by Changes in the Repertoire of Transport Proteins in the Plasma Membrane 299
V. Coordinated Regulation of Transport Systems 302
VI. Derangements in Transport Regulation 302
VII. Summary 308
Chapter 10. Biomembrane Transport and Interorgan Nutrient Flows: The Amino Acids 310
I. Interorgan Nutrition 310
II. Interorgan Amino Acid Nutrition: General Principles and Key Issues 310
III. Control of Interorgan Amino Acid Metabolism: Metabolic Control Theory and Safety Factors 323
IV. Physiologically Important Flows of Amino Acids and Related Compounds 326
V. Amino Acid Nutrition under Special Circumstances 334
VI. Summary 340
Chapter 11. Selected Techniques in Membrane Transport 342
I. Introduction 342
II. Purification and Reconstitution of Transport Proteins 342
III. Methods for Isolating cDNAs Coding for Transport Proteins 343
IV. Heterologous Expression Systems for Transport Proteins 344
V. Voltage-Clamp Techniques in Xenopus Oocytes 347
VI. Probing Transport with Ion-Selective Microelectrodes 353
VII. Optical Methods for Measuring Membrane Transport 354
VIII. Structure-Function Studies of Transport Proteins 354
IX. Genetic Approaches to Understanding Transporter Function 356
X. Summary of Preparations Used to Study Native Membrane Transport 356
XI. Commentary 357
Epilogue 358
References 360
Index 402