Biochemistry of Lipids,Lipoproteins and Membranes

Editors

DENNIS E. VANCE and JEAN E. VANCE

Lipid and Lipoprotein Research Group, Faculty of Medicine,328 Heritage Medical Research Centre, Edmonton, Aha., Canada, T6G 2S2

1991ELSEVIER

Amsterdam • London • New York • Tokyo

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ContentsPreface v

List of contributors vii

Chapter 1. Physical properties and functional roles of lipids in membranes

Pieter R. Cullis and Michael J. Hope l

1. Introduction and overview 12. Lipid diversity and distribution 3

2.1. Chemical diversity of lipids 32.2. Membrane lipid compositions 52.3. Transbilayer lipid asymmetry 7

3. Model membrane systems 83.1. Lipid isolation and purification 93.2. Techniques for making model membrane vesicles 93.3. Techniques for making planar bilayers and monolayers 133.4. Reconstitution of integral membrane protein into vesicles 13

4. Physical properties of lipids 154.1. Gel-liquid-crystalline phase behaviour 154.2. Lipid polymorphism 194.3. Factors which modulate lipid polymorphism 244.4. The physical basis of lipid polymorphism 26

5. Lipids and the permeability properties of membranes 285.1. Theoretical considerations 285.2. Permeability of water and non-electrolytes 295.3. Permeability of ions 30

6. Lipid-protein interactions 316.1. Extrinsic proteins 326.2. Intrinsic proteins 33

7. Lipids and membrane fusion 347.1. Fusion of model systems 347.2. Fusion of biological membranes 36

8. Model membranes and drug delivery 389. Future directions 40References 40

Chapter 2. Lipid metabolism in procaryotesS. Jackowski, J.E. Cronan Jr. and CO. Rock 43

1. The study of bacterial lipid metabolism 432. Historical introduction 433. An overview of phospholipid metabolism in E. coli 444. Genetic analysis of lipid metabolism 445. Membrane systems of E. coli 48

6. Lipid biosynthetic pathways in E. coli 506.1. Initiation of fatty acid biosynthesis 506.2. Elongation of acyl chains 516.3. Product diversification 526.4. Transfer to the membrane 536.5. Diversification of polar head groups 546.6. Central role of acyl carrier protein 54

7. Lipopolysaccharide biosynthesis 588. Degradative pathways 59

8.1. Phospholipases 598.2. Thioesterases 628.3. Fatty acid oxidation in bacteria 63

9. Phospholipid turnover 639.1. The diacylglycerol cycle 639.2. The 2-acylglycerolphosphoethanolamine cycle 65

10. Inhibitors of lipid metabolism 6610.1. 3-Decynoyl-yV-acetylcysteamine 6610.2. Cerulenin 6610.3. Thiolactomycin 67

11. Regulation of fatty acid composition in E. coli 6811.1. Role of 3-hydroxydecanoyl-ACP dehydrase 6811.2. Role of 3-ketoacyl-ACP synthase I 6911.3. Role of 3-ketoacyl-ACP synthase II 7011.4. Factors affecting fatty acid chain-length distribution 7211.5. Synthesis of cyclopropane fatty acids 7211.6. Importance of the fatty acid composition of the membrane phospholipids . . . 73

12. Regulation of phospholipid biosynthesis in E. coli 7412.1. Control of fatty acid positional distribution 7412.2. Regulation of total phospholipid synthesis 7612.3. Coordination of phospholipid synthesis with cellular metabolism 7712.4. Regulation of phospholipid head group composition 7712.5. E. coli tolerates variations in phospholipid composition 7812.6. Outer membrane lipoprotein 79

13. Lipid metabolism in bacteria other than E. coli 8013.1. Bacteria lacking unsaturated fatty acids 8013.2. Bacteria containing phosphatidylcholine 8113.3. Bacteria synthesizing unsaturated fatty acids by an aerobic pathway 8113.4. Bacteria with a multifunctional fatty acid synthase 8113.5. Bacteria with intracytoplasmic membranes 8213.6. Other bacterial oddities 8213.7. Lipids of nonbacterial (but related) organisms 83

14. Future directions 83References 84

Chapter 3. Oxidation of fatty acidsHorst Schulz 87

1. The pathway of ^-oxidation: a historical account 872. Uptake and activation of fatty acids in animal cells 89

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3. ^-Oxidation in mitochondria 913.1. Mitochondrial uptake of fatty acids 913.2. Enzymes of /J-oxidation in mitochondria 933.3. /^-Oxidation of unsaturated and odd-chain fatty acids 963.4. Regulation of mitochondrial /J-oxidation 983.5. Inhibitors of mitochondrial /7-oxidation 100

4. /J-Oxidation in peroxisomes 1015. Fatty acid oxidation in E. coli 1046. Inherited diseases of fatty acid oxidation 1067. Future directions 108References 109

Chapter 4. Fatty acid synthesis in eucaryotesAlan G. Goodridge ill

1. Introduction Il l2. Signals in blood that mediate the effects of diet 1123. Which enzymes regulate fatty acid synthesis? 1144. Regulation of substrate supply 115

4.1. Production of pyruvate from glucose 1154.2. Production of citrate from pyruvate 1154.3. Production of NADPH 117

5. Regulation of the catalytic efficiency of acetyl-CoA carboxylase 1175.1. A key regulatory reaction 1175.2. Structure and reaction mechanism 1185.3. Regulation by citrate 1185.4. Regulation by long-chain fatty acyl-CoA 1195.5. Regulation by covalent modification 121

6. Fatty acid synthase 1256.1. Animal fatty acid synthase: the component reactions 1256.2. Animal fatty acid synthase: the subunits are identical 1276.3. Animal fatty acid synthase: structural organization 1286.4. Comparison of yeast and animal fatty acid synthases 129

7. Regulation of enzyme concentration 1307.1. Messenger RNA levels regulate enzyme synthesis rates 1307.2. Transcription is usually the regulated step 1317.3. Regulation in cells in culture 134

7.3.1. 3T3-L1 cells —a pre-adipocyte cell line 1347.3.2. Hepatocytes in maintenance culture 135

8. Future directions 137References 138

Chapter 5. Fatty acid desaturation and chain elongation in eucaryotesHarold W. Cook 141

1. Introduction 1412. Historical background 1433. Chain elongation of long chain fatty acids 144

Xl l

3.1. The microsomal elongation system 1463.2. The mitochondrial elongation system 1473.3. Functions of the two elongation systems 148

4. Formation of monounsaturated fatty acids by oxidative desaturation 1484.1. Nomenclature to describe double bonds 1484.2. Characteristics of the monoene-forming desaturation enzymes 1494.3. Modification of zl9 desaturase activities in vitro 1514.4. Dietary and hormonal regulation of J9 desaturase 1524.5. Formation of monounsaturated fatty acids in plants 154

5. Formation of polyunsaturated fatty acids 1545.1. Characteristics and restrictions in animal systems 1545.2. Essential fatty acids—a contribution of plant systems 1555.3. Families of fatty acids and their metabolism 157

5.3.1. The (n-6) family 1575.3.2. The (n-3) family 1595.3.3. Competition between the (n-6) and (n-3) families 1605.3.4. The (n-9) family 1615.3.5. The (n-7) family 161

5.4. Dietary and hormonal alterations of polyunsaturated acid synthesis 1615.5. Two or more double bonds in plants 163

6. Unsaturated fatty acids with trans double bonds 1647. Abnormal patterns of distribution and metabolism of long chain saturated and unsaturated

fatty acids 1657.1. Essential fatty acid deficiency 1657.2. Zinc deficiency 1667.3. Other clinical disorders 1667.4. Relationship to plasma cholesterol 166

8. Future directions 167References 168

Chapter 6. Metabolism of triacylglycerolsDavid N. Brindley 171

1. Introduction 1712. Biosynthesis of triacylglycerols 173

2.1. Biosynthesis of phosphatidate 1732.2. Conversion of phosphatidate to triacylglycerol 1782.3. Conversion of monoacylglycerol to triacylglycerol 179

3. Digestion, absorption and transport of lipids 1813.1. Digestion of lipids 1813.2. Absorption of lipids from the small intestine 1833.3. Formation of chylomicrons and VLDL 1843.4. Partitioning of fatty acids between the portal blood and the lymphatic system . . 186

4. Control of triacylglycerol synthesis 1874.1. Control of phosphatidate synthesis in the liver 1884.2. Control of the conversion of phosphatidate to triacylglycerol in liver 1894.3. Diacylglycerol as a precursor of triacylglycerol, phosphatidylcholine and phosphati-

dylethanolamine 1935. Metabolism of triacylglycerols when the action of insulin is high 1956. Triacylglycerol metabolism in conditions of metabolic stress 198

Xl l l

7. Future directions 200References 201

Chapter 7. Phospholipid metabolism and cell signalling in eucaryotesDennis E. Vance 205

1. Introduction 2052. Phosphatidylcholine biosynthesis 206

2.1. Historical background 2062.2. Choline transport and oxidation 2072.3. Enzymes of the CDP-choline pathway 2072.4. Phosphatidylethanolamine-JV-methyltransferase 208

3. Regulation of phosphatidylcholine biosynthesis 2093.1. The rate-limiting reaction 2093.2. The translocation hypothesis 2103.3. Regulatory mechanisms 210

3.3.1. Fatty acids are important regulators of phosphatidylcholine biosynthesis incultured cells 211

3.3.2. Diacylglycerol may also regulate phosphatidylcholine biosynthesis . . . 2113.3.3. Phosphorylation-dephosphorylation reactions 2123.3.4. Feedback regulation 2123.3.5. Cholinephosphotransferase 213

3.4. Substrate channeling 2134. Sphingomyelin biosynthesis 2145. Phosphatidylserine biosynthesis 215

5.1. Historical developments and biosynthesis 2155.2. CHO mutants and regulation 217

6. Phosphatidylethanolamine biosynthesis 2186.1. Historical background 2186.2. Enzymes of the CDP-ethanolamine pathway 2186.3. Regulation of the CDP-ethanolamine pathway 219

6.3.1. Regulation at the cytidylyltransferase reaction 2196.3.2. Diacylglycerol 220

6.4. Phosphatidylserine decarboxylation and the relative importance of the variouspathways for phosphatidylethanolamine biosynthesis 221

6.5. JV-acyl-phosphatidylethanolamine 2217. Polyglycerophospholipids 222

7.1. Historical developments and biosynthetic pathways 2227.2. Enzymes and subcellular location 224

8. Inositol phospholipids 2248.1. Historical developments 2248.2. Biosynthetic enzymes 225

9. Phospholipids as precursors of cellular second messengers 2269.1. Discovery of the phosphatidylinositol cycle 2269.2. Degradation of phosphatidylinositol-4,5-bisphosphate by phospholipaseC . . . 2279.3. Metabolism of the inositol phosphates 2289.4. Function of inositol phosphates 2299.5. Diacylglycerol and protein kinase C 2309.6. Phosphatidylcholine cycles and formation of diacylglycerol 231

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10. Phospholipid catabolism and remodeling of the acyl substituents 231

11. Phospholipid biosynthesis in yeast 23312. Phosphonolipids 234

12.1. Historical perspective 23412.2. Biosynthesis 235

13. Glycosyl phosphatidylinositols for attachment of cell surface proteins 236

14. Future directions 238References 2 3 8

Chapter 8. Metabolism, regulation, and function of ether-linked glycerolipids and

their bioactive speciesFredSnyder 241

1. Introduction 2412. Nomenclature 2413. Historical events 2434. Analytical approaches 2455. Physical properties 2476. Occurrences in nature 2487. Biologically active ether lipids 2498. Biosynthesis 250

8.1. Ether lipid precursors 2508.1.1. Acyl-CoA reductase 2508.1.2. Dihydroxyacetone-P acyltransferase 250

8.2. Ether lipids in membranes 2528.2.1. Biosynthesis of the ether bond 2528.2.2. Biosynthesis of the alkyl analogue of phosphatidic acid 2548.2.3. Biosynthesis of complex neutral glycerolipids and phospholipids with 0-alkyl

bonds 2548.2.4. Biosynthesis of plasmalogens 255

8.3. Bioactive ether lipids 2569. Catabolism 258

9.1. Ether lipid precursors 2589.1.1. Long-chain fatty alcohols 2589.1.2. Dihydroxyacetone-P and acyldihydroxyacetone-P 258

9.2. Ether lipids in membranes 2599.2.1. Alkyl cleavage enzyme 2599.2.2. Plasmalogenases 2609.2.3. Phospholipases and lipases 260

9.3. Bioactive ether lipids 26210. Regulatory controls 26311. Functional roles 264

11.1. Membrane components 264

11.2. Cell mediators (activities and mechanisms of action) 26512. Future directions 266References 267

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Chapter 9. Phospholipases

Moseley Waite 269

1. Overview 269

1.1. Definition of phospholipases 2691.2. Assay of phospholipases 2711.3. Interaction of phospholipases with interfaces 272

2. The phospholipases 2762.1. Phospholipase A2 2762.2. Phospholipase B and lysophospholipases 2782.3. Phospholipase A2 2802.4. Phospholipase C 2872.5. Phospholipase D 2902.6. Phospholipases in signal transduction 292

3. Future directions 292References 294

Chapter 10. The eicosanoids: cyclooxygenase, lipoxygenase, and epoxygenasepathwaysWilliam L. Smith, Pierre Borgeat and Frank A. Fitzpatrick 297

1. Introduction 2972. Prostanoids 298

2.1. Structures and nomenclature 2982.2. Prostanoid chemistry 2992.3. Prostanoid biosynthesis 2992.4. Arachidonate release 2992.5. Prostaglandin endoperoxide formation 3002.6. Physico-chemical properties of PGH synthase 3022.7. PGH synthase and nonsteroidal anti-inflammatory drugs 3022.8. Anti-inflammatory steroids 3032.9. PGH synthase active site 3042.10. Regulation of PGH synthase gene expression 3042.11. PGH2 metabolism 3052.12. Catabolism: prostanoids as local hormones 306

3. Hydroxy- and hydroperoxy-eicosaenoic acids and leukotrienes 3083.1. Introduction and overview 3083.2. Mechanism of leukotriene biosynthesis in human neutrophils 3093.3. The enzymes of the 5-lipoxygenase pathway 3123.4. Regulation of leukotriene synthesis 3133.5. The metabolism of lipoxygenase products 3153.6. Biological activities of leukotrienes 317

4. Epoxygenase products 3184.1. Introduction 3184.2. Structures, nomenclature, and biosynthesis 3184.3. Occurrence of epoxyeicosatrienoic acids 3214.4. Metabolism of epoxygenase metabolites of arachidonic acid 3214.5. Biological actions of 'epoxygenase' derived EpETrEs and HETrEs 322

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5. Future directions 3225.1. Cyclooxygenase metabolites 3225.2. Lipoxygenase metabolites 3235.3. Epoxygenase metabolites 323

References 323

Chapter 11. SphingolipidsCharles C. Sweeley 327

1. Introduction 3272. Chemistry and distribution 330

2.1. Sphingoid bases 3302.2. Ceramides 3322.3. Glycosphingolipids 333

2.3.1. Neutral glycosphingolipids 3332.3.2. Acidic glycosphingolipids 3342.3.2.1. Gangliosides 3342.3.2.2. Phosphorus-containing glycosphingolipids 3362.3.2.3. Sulfatoglycosphingolipids 337

3. Biosynthesis of sphingolipids 3373.1. Sphingoid bases and ceramide 3383.2. Sphingomyelin 3403.3. Sulfatoglycosphingolipids 3403.4. Neutral glycosphingolipids 341

3.4.1. Cell surface glycosyltransferases 3453.5. Gangliosides 345

4. Turnover of sphingolipids 3474.1. Lysosomal metabolism of sphingolipids 348

4.1.1. Sphingomyelin 3484.1.2. Ceramide 3494.1.3. Glycosphingolipids 349

4.2. Glycosphingolipid storage diseases 3504.2.1. Tay-Sachs disease and related disorders 3514.2.1.1. a-Subunit mutations 3524.2.1.2. /?-Subunit mutations 3534.2.1.3. Defective GM2 activator protein 3534.2.2. Fabry's disease and Schindler's disease 353

5. Regulation of glycosphingolipid metabolism 3545.1. Developmental changes 355

5.1.1. Glycosphingolipid markers in leukocyte differentiation 3555.1.2. Early embryonic markers 356

5.2. Oncogenic transformation and immunomodulation by shed gangliosides . . . . 3566. Biological activities and functional roles of sphingolipids 357

6.1. Adherence of microorganisms to cell surface glycosphingolipids 3576.2. Modulation of signal transduction 358

6.2.1. Glycosphingolipids 3586.2.2. Sphingoid bases 359

7. Future directions 359References 360

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Chapter 12. Cholesterol: evolution of structure and functionKonrad Bloch 363

1. Natural occurrence of sterols 3632. Metabolic and precursor functions of the sterol molecule 3643. Sterol patterns 3664. Sterols and membrane function 368

4.1. Function of sterols in animal membranes 3684.2. Sterol auxotrophs 3694.3. Metabolic regulation in the membrane environment 3704.4. Fluidity control 371

5. Regulatory roles for sterols in membranes 3725.1. Fungi and invertebrates 3725.2. Sterol effects on hormone and neurotransmitter receptors 3735.3. Sterols and fusion of viral membranes 3745.4. Capping of surface immunoglobulin 3755.5. Sterol effects on enzyme activities 3755.6. Effects of cholesterol on phospholipid synthesis 376

6. Evolution of the sterol structure 3777. Future directions 380References 381

Chapter 13. Regulation of sterol biosynthesis and isoprenylation of proteinsPeter A . Edwards 383

1. Introduction 3 8 3

2. Regulation of cholesterol synthesis 3 8 5

3. Regulation of cholesteryl ester synthesis 3 8 7

4. Transcriptional control of cholesterol synthesis 3 8 9

5. Posttranscriptional regulation6. Identification of the physiological regulators1. Regulation of bile acid synthesis8. Isoprenylation of proteins9. Future directionsReferences 4 0 0

Chapter 14. Lipoprotein structure and secretionRoger A . Davis 403

1- Introduction2. Structure and function of plasma lipoproteins

2.1. Chylomicrons and very low density lipoproteins

2.2. Structure: surface components „ .

2.3. Core components 4QS

2.4. Low density lipoproteins: structure ^2.4.1. Origin of low density lipoproteins ^2.4.2. High density lipoproteins: structure and function ^

2.4.3. Discoidal high density lipoproteins

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3. Assembly of nascent lipoproteins 4113.1. Triacylglycerol-rich lipoproteins 411

3.1.1. Role of lipids 4123.2. Core lipids 412

3.2.1. Role of apolipoproteins 4133.2.2. Apolipoprotein B structure 413

3.3. Vitellogenin: the primordial apolipoprotein 415

3.4. Very low density lipoprotein assembly: ejection of a ball of fat out of the endoplasmic

reticulum '*' '3.5. Filling the hydrophobic core: a thermodynamic dilemma 4223.6. High density lipoprotein synthesis and secretion 422

4. Future directions 423References 424

Chapter 15. Dynamics of lipoprotein transport in the circulatory systemPhoebe E. Fielding and Christopher J. Fielding 427

1. Overview 4272. Lipoprotein lipase and the initial metabolism of lipoprotein triacylglycerol 430

2.1. Initial events 4302.2. Lipoprotein lipase structure 4312.3. Synthesis and transport of lipoprotein lipase 4312.4. The lipoprotein lipase reaction and the role of apolipoprotein C-2 4322.5. Lipoprotein lipase activity at the vascular surface 4342.6. Regulation of lipoprotein lipase activity by products of lipolysis 4352.7. Physiological regulation of lipoprotein lipase 4362.8. Congenital lipoprotein lipase deficiency 437

3. Hepatic triacylglycerol lipase and the later metabolism of lipoprotein triacylglycerol. . . 4373.1. Introduction 4373.2. Structure of hepatic triacylglycerol lipase 4373.3. Acyl group hydrolysis and exchange catalyzed by hepatic triacylglycerol lipase . . 4383.4. Hepatic triacylglycerol lipase and the hydrolysis of lipoprotein lipids 4383.5. Regulation of hepatic triacylglycerol lipase activity 4393.6. Human hepatic triacylglycerol lipase deficiency 4403.7. Phospholipid exchange protein and its activity 440

4. Lecithin:cholesterol acyltransferase and the initial metabolism of lipoprotein cholesterol . 4404.1. Introduction 4404.2. 'Forward' cholesterol transport by very low density lipoprotein and its product, low

density lipoprotein 4444.3. Origin of the major high density lipoprotein proteins 4454.4. Classification of plasma and lymph high density lipoprotein 4464.5. Apoprotein transfers in high density lipoprotein 4464.6. Origin of plasma lecithin:cholesterol acyltransferase 4474.7. Structure of plasma lecithin:cholesterol acyltransferase 4474.8. Mechanism of plasma lecithinxholesterol acyltransferase activity 4484.9. Role of apo A-l in the plasma lecithin:cholesterol acyltransferase reaction . . . 4494.10. Transfer of cholesterol among high density lipoprotein species 4504.11. Physiological regulation of plasma lecithinxholesterol acyltransferase activity . . 4524.12. Studies of plasma lecithinxholesterol acyltransferase deficiency 452

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5. Cholesteryl ester transfer protein and the later metabolism of lipoprotein cholesterol . . 4525.1. Introduction 4525.2. Structure of cholesteryl ester transfer protein 4545.3. Mechanism of cholesteryl ester transfer protein activity 4545.4. Quantitation of cholesteryl ester transfer 4565.5. Physiological regulation of cholesteryl ester transfer protein 4565.6. Congenital cholesteryl ester transfer protein deficiency 4575.7. Cholesteryl ester transfer protein inhibitor protein 457

6. Summary and future directions 457References 458

Chapter 16. Removal of lipoproteins from plasmaWolfgang J. Schneider 461

1. Introduction 4612. Removal of low density lipoprotein from the circulation 464

2.1. Receptor-mediated endocytosis 4642.2. The low density lipoprotein receptor pathway 465

2.2.1. Familial hypercholesterolemia: clinical consequences of low density lipo-protein receptor dysfunction 466

2.2.2. Biochemical findings in cultured fibroblasts from familial hypercholest-erolemia homozygotes 467

2.3. Biosynthesis and structure of the low density lipoprotein receptor 4672.3.1. The low density lipoprotein receptor protein 4682.3.2. The ligand binding domain 4692.3.3. The EGF precursor homology domain 4702.3.4. The third domain 4702.3.5. The membrane anchoring domain 4702.3.6. The cytoplasmic tail 471

2.4. Molecular defects in low density lipoprotein receptors of patients with familial hyper-cholesterolemia 4712.4.1. The gene for the human low density lipoprotein receptor 4712.4.2. Four groups of low density lipoprotein receptor mutations 4722.4.2.1. Class 1: no detectable precursor 4722.4.2.2. Class 2: slow or absent processing of precursor 4722.4.2.3. Class 3: abnormal ligand binding 4732.4.2.4. Class 4: internalization defective 474

3. Catabolism of chylomicrons 4754. High density lipoprotein as a transport vehicle 4775. Atherosclerosis 478

5.1. Uptake and modification of low density lipoprotein in the intima 478

5.2. Scavenger receptors 4806. Lipoprotein transport in the laying hen 4817. Low density lipoprotein metabolism by rat serosal mast cells 483

8. Future directions 485References 485

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Chapter 17. Lipid assembly into cell membranesDennis R. Voelker 489

1. Introduction 4892. The diversity of lipids 4893. Methods to study intra- and inter-membrane lipid transport 492

3.1. Fluorescent probes 4943.2. Spin labeled analogs 4943.3. Asymmetric chemical modification of membranes 4953.4. Phospholipid transfer proteins 4963.5. Rapid plasma membrane isolation 4973.6. Organelle specific lipid metabolism 498

4. Lipid transport processes 4984.1. Intramembrane lipid translocation and model membranes 4984.2. Intramembrane lipid translocation and biological membranes 502

4.2.1. Procaryotes 5024.2.2. Eucaryotes 5034.2.2.1. Transbilayer movement at the endoplasmic reticulum 5034.2.2.2. Transbilayer movement of phosphatidylcholine in erythrocytes . . . . 5044.2.2.3. Transbilayer movement of phosphatidylcholine in nucleated cells . . . 5054.2.2.4. ATP dependent transbilayer movement of aminophospholipids at the plasma

membrane of eukaryotic cells 5064.3. Intermembrane lipid transport 507

4.3.1. Transport in procaryotes 5074.3.2. Transport in eucaryotes 5104.3.2.1. Phosphatidylcholine 5104.3.2.2. Phosphatidylethanolamine 5124.3.2.3. Phosphatidylserine 5134.3.2.4. Sphingolipids 5154.3.2.5. Cholesterol 5174.3.2.6. Phospholipid transfer proteins and phosphatidylinositol transport . . . 518

5. Future directions 521References 522

Chapter 18. Assembly of proteins into membranesReinhart A.F. Reithmeier 525

1. Organization of membrane proteins 5251.1. Classification of membrane proteins 5251.2. Membrane protein structure and energetics 5281.3. Assembly of membrane proteins 530

2. Secretion of proteins and the signal hypothesis 5322.1. The Palade secretion pathway 5332.2. The Blobel signal hypothesis 5332.3. In vitro translation and translocation systems 5352.4. The Milstein experiment: secreted proteins are made with an amino terminal signal

sequence 5382.5. Signal sequences 540

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3. The targeting and translocation machinery 5413.1. The signal recognition particle 5423.2. The signal recognition particle receptor 5433.3. Translocation components 5443.4. Ribosome-binding proteins 5453.5. Signal peptidase 546

4. Biosynthesis of type I simple membrane proteins 5464.1. IgM and the relationship between the biosynthesis of secreted proteins and simple

membrane proteins 5464.2. Vesicular stomatitis virus glycoprotein and hemagglutinin 5494.3. Loop models and insertion into the lipid bilayer 5514.4. Evidence for a loop structure for insertion of signal sequences 553

5. Biosynthesis of type II simple membrane proteins 5545.1. Ovalbumin, a secreted protein made without a cleaved signal sequence . . . . 5565.2. Asialoglycoprotein receptor 5575.3. Sucrase-isomaltase 557

6. Biosynthesis of cytochrome P-450 and cytochrome b5 5586.1. Cytochrome P-450 5586.2. Cytochrome b5 559

7. Biosynthesis of complex membrane proteins 5597.1. Artificial membrane proteins 5597.2. Band 3, the anion transport protein of the erythrocyte membrane 5617.3. Glucose carrier 5617.4. Rhodopsin 5617.5. Ca2+ ATPase and calsequestrin 562

8. Glycosylation of proteins 5628.1. JV-glycosylation 5628.2. Processing of the oligosaccharide chain 5638.3. O-glycosylation 566

9. Attachment of lipid to proteins 5669.1. Fatty acylation 5669.2. Phosphatidylinositol anchors 567

10. Protein folding and exit from the endoplasmic reticulum 567

10.1. Protein folding 56710.2. Disulfide formation 56810.3. Assembly of multisubunit systems 56910.4. Exit from the endoplasmic reticulum 57010.5. KDEL, an endoplasmic reticulum retention signal 570

11. Transport and targeting of proteins 57111.1. Vesicles move proteins between organelles 57111.2. Role of GTP-binding proteins 57311.3. Lysosomal targeting 57511.4. Protein sorting in epithelial cells 576

12. Future directions - ^References 577

Index 579