Biomembranes

Both science and religion are aspects of human endeavor that do not observe political constraints. It is therefore appropriate that contributions should come from many different countries for a series which attempts to chronicle developments in an interdisciplinary field such as membrane research. This volume is an excellent example of the diversity of thinking, background, and approach needed by the working scientist for his re­ search planning. From Canada comes a review by Silverman and Turner of the mech­ anisms by means of which the plasma membrane of the renal proximal tubule acts as a transport mediator. The two chapters that were writtyn by American scientists are excellent examples of the comparative bio­ chemical approach. Inouye feels he must apologize for being interested in the outer membrane of E. coli, but it is obvious, after a reading of his chapter, that no apology is required. On the contrary, we are grateful for his drawing our attention to this system and its unique properties. Holtz­ man, Gronowicz, Mercurio, and Masur are also on a consciousness­ raising mission in summarizing for us a number of integrated functions of membranes using the toad bladder as an experimental system. The other two chapters of this volume come from overseas. N orthcote has again demonstrated his capacity to integrate a complex and difficult field.

Contenu

1 The Renal Proximal Tubule.- I. Introduction.- II. Morphologic Asymmetry.- III. Biochemical Asymmetry.- IV. Transport Asymmetry.- A. Sugar Transport.- B. Amino Acid Transport.- C. Phosphate Transport.- D. Uric Acid Transport.- E. Lactate Transport.- F. Paraaminohippurate Transport.- G. Anion Channels.- V. Interdependence of Tubular Transport Systems.- VI. Hormone Receptors.- VII. Structural Determinants of Epithelial Plasma Membrane Asymmetry.- VIII. Proximal Tubule Dysfunction.- A. Type I-Altered Gene Product.- B. Type II-The Fanconi Syndrome-Disorder of Membrane Energization.- C. Homology between Red Cell Membrane and the Antiluminal Membrane of the Renal Proximal Tubule.- IX. Conclusion.- X. References.- 2 The Involvement of the Golgi Apparatus in the Biosynthesis and Secretion of Glycoproteins and Polysaccharides.- I. Introduction.- II. Polysaccharide and Glycoprotein Formation.- A. Transport of Initial Glycosyl Donors to the Lumen of the Endomembrane System.- B. Assembly of Sugar Polymers on Intermediate Carriers.- C. Types of Glycoprotein and Polysaccharide Formed by the Endomembrane System.- D. Assembly of Complexes within the Golgi Apparatus.- III. Transport of the Polymers from the Endomembrane System.- A. Transport as Lipoglycoprotein.- B. Transport of Vesicles.- IV. Membrane Fusion.- A. Biochemistry of Membranes at Fusion.- B. Ultrastructure of the Membranes at Fusion.- C. Ultrastructure during the Formation of Transport Vesicles from Membranes.- D. The Fusion Process.- E. Membrane Recycling.- V. Control of Polysaccharide Formation for Secretion.- A. Formation of the Golgi Apparatus.- B. Membrane Differentiation and Change in the function of the Golgi Apparatus.- C. Control of the Activity of the Golgi Apparatus by Enzymic Regulation.- D. Control of Vesicle Fusion at the Plasma Membrane.- VI. References.- 3 Notes on the Heterogeneity, Circulation, and Modification of Membranes, with Emphasis on Secretory Cells, Photoreceptors, and the Toad Bladder.- I. Introduction.- II. Membrane Heterogeneity and the Endoplasmic Reticulum.- A. Lateral Heterogeneity in the Plasma Membrane.- B. Heterogeneity in the Endoplasmic Reticulum.- C. Three Zones of Smooth ER in Retinal Photoreceptors.- D. The Membranes of ER-Derived Organelles.- III. Membrane Diversification.- A. Bulk Transport Phenomena.- B. Specificity of Membrane Growth and Assembly.- C. Selective Redistribution of Membrane Constituents.- D. Ongoing Studies of Membrane Modification: Microorganisms and the Toad Bladder.- IV. Concluding Comments.- V. References.- 4 Lipoprotein of the Outer Membrane of Escherichia coli.- I. Introduction.- A. Is the Outer Membrane Foreign to You?.- B. What Is the Outer Membrane?.- II. Structure.- A. Bound Form of the Lipoprotein.- B. Free Form of the Lipoprotein.- C. Location and Amount of the Lipoprotein.- D. Conformation of the Lipoprotein.- III. Biosynthesis.- A. Specific Biosynthesis in Vivo.- B. Effects of Antibiotics.- C. Cell-Free Synthesis.- D. Prolipoprotein: Precursor of the Lipoprotein.- E. Structure of the Lipoprotein mRNA.- IV. Modification and Assembly.- A. Posttranslational Modification.- B. Molecular Assembly Models.- C. Interactions with Other Proteins.- D. Effects of Lipid Fluidity.- E. In Vitro Assembly.- V. Genetic Approaches.- A. Isolation of Mutants of the Lipoprotein.- B. Gene-Dosage Effects.- C. Genetic Engineering.- D. Other Gram-Negative Bacteria.- VI. Other Approaches.- A. Electron Spin Resonance (ESR); Nuclear Magnetic Resonance (NMR).- B. Mitogenic Activity.- C. Identification of Lysozyme Specificity.- VII. Conclusions.- VIII. References.- 5 Electrochemical Proton Gradient across the Membranes of Photophosphorylating Bacteria.- I. Introduction.- II. Electrochemical Potential Gradient across the Chromatophore Membrane.- A. Registration of Electric Potential Difference.- B. Registration of the Transmembranous Difference of Proton Concentrations.- III. Electrochemical Potential Gradient across the Bacteriorhodopsin Membrane.- A. Characteristics of Bacteriorhodopsin.- B. Registration of the Electrochemical Potential Gradient.- C. Proton Binding and Release during the Photoreaction Cycle.- IV. Functions of the Transmembrane Electrochemical Potential Gradient.- A. Energy Pool.- B. Polyfunctional Regulator.- V. Addendum.- VI. References.