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The enzymes of biological membranes Vol. l. Physical and chemical techniques
TIBS - April 1977
94
Membrane proteins, where are you? The Enzymes of Biological branes Vol. I. Physical and Chemical Techniques
Mem-
edited by A. Martonosi, published by Plenum Press, New York, 1976. (257 pages)
Question: How do you write about a subject that does not exist? Answer: Either you write about the subject as you think it might exist in the future or else you write about something else. Unfortunately, it is the latter alternative that has generally been adopted in this volume. For a wide variety of fairly obvious technical reasons, virtually nothing is known about the molecular structure of membrane-bound proteins. This is contirmed by a reading of this book. Indeed, the book contains only one picture of a membrane protein : rhodopsin pictured as a rather lop-sided dumb-bell. The bulk of the reviews are concerned in fact with spectroscopic studies of lipids in model systems or in intact membranes, an interesting but much reviewed topic. In the first chapter Worthington reviews X-ray diffraction studies of membranes, and amply illustrates the difficulties associated with the correct choices of phase and correction factors. This leaves the general reader in something of a quandary. Thus the correct location for rhodopsin in the disc membrane has undoubtedly been determined by X-ray diffraction, undoubtedly because all possible locations have been proposed by one group of workers or another. The second chapter is a long review by Urry on nuclear magnetic resonance studies of the conformations of small peptides in organic solution, and discusses neither proteins nor membranes. This is then followed by two chapters on electron spin resonance by Gaffney, Lin, Vignais and Devaux. Overlap between the two chapters is considerable, both including discussion of the effects of solvent polarity and fluidity on spectra and concentrating on changes in membrane lipids. Next, Waggoner presents a very interesting review of fluorescence probe studies of membranes, but again discussion is of the membrane as a whole, and particularly its lipid component, rather than ofmembrane proteins. Tien and Mountz then convincingly demonstrate that nothing has been learnt about membrane proteins from studies with black lipid films. Discussion of membrane proteins really starts with the chapter by Tinberg and
Packer. They present a very stimulating review on chemical modification of membrane proteins, the technique which has given most information on three-dimensional structure. A technique withmuch promise, the use ofspecific antibodies, is discussed by Kyte. The two remaining chapters by Mavis and Gittler respectively deal with the effects of lipids on the activity of membrane bound proteins and the nature of lipid-protein interactions. All in all this book is rather disappointing, not as regards to any individual contribution but rather to the chosen topic for the volume. Despite much work and 257 pages the picture of a membrane protein that is left to haunt our dreams is of the lop-sided dumb-bell. A. G. LEE A. C. Lee is lecturer in the Department of Physiology and Biochemistry, University of Southampton, Southampton, U.K.
Toxic polypeptides Animal, Plant and Microbial Toxins : Vol. 1, Biochemistry ; Vol. 2, Chemistry, Pharmacology and Immunology edited by Akira Ohsaka, Kyozo Hayashi and Yoshio Sawai, published by Plenum Press, New York and London, 1976. Vol. I, $10.80 (approx. &5.-) (xxvi+.555 pages); Vol. 2, $10.80 (approx. &5.-) (xxv + 562 pages)
In these two volumes are published the proceedings of the Fourth International Symposium on Animal, Plant and Microbial Toxins held in Tokyo, Japan, 8-13 September, 1974. About half of all the chapters deal with the structure and pharmacological action of toxic polypeptides isolated from the venoms of snakes and scorpions. During the past few years more than 40 ‘neurotoxins’ and ‘cardiotoxins’ have been isolated from the venoms of Hydropidae and Elapidue snakes (sea snakes, cobras, kraits, etc.) and their primary structures have been determined. All of them, whether classified as neurotoxins or as cardiotoxins, have molecular weights between 7000 and 8000, contain either 4 or 5 intrachain disulfide bridges and show striking similarities in their amino acid sequence. The neurotoxins are of considerable interest to biologists because of their post-synaptic curare-like action and because they interact with and block cholinergic receptor sites. Progress on the chemical synthesis of toxic polypeptides is reported from two laboratories. Using the solid-phase techniques of Merrilield, N.
Izumya and his colleagues in Tokyo have synthesized a 62-amino acid polypeptide with about 6 % of the toxicity of cobra cardiotoxin. In the following chapter, V.T. Ivanov reports the use of classical techniques to synthesize 11 short polypeptides totalling 74 amino acids, which when joined together should yield r-bungarotoxin of the Taiwanian krait. Several chapters deal with similarities between toxins isolated from various species of scorpions and from cobra cardiotoxins. The toxic polypeptides isolated from both scorpion venoms and from snake venoms have molecular weights of about 7000, contain four intrachain disulfide linkages and unlike the typical snake ‘neurotoxins’, both act directly on the motor nerves to induce neuromuscular blockade and membrane depolarization. Snake venoms have long been known to contain many toxic enzymes of interest to the biochemist. First, I will deal with the proteases. Most snake bites cause hemorrhage at the site of injection into mammals. Mandelbaumetal. have isolated an hemorrhagic protease from Bothrops jararaca which cleaves four peptide bonds of the insulin B chain as follows : His-Leu (l& ll), Ala-Leu (1415), Trp-Leu (16-17) and Phe-Phe (24-25). The protease has almost no caseinolytic activity. Prescott et al. have studied proteases with similar specificity which they isolated from other species. In an interesting chapter, A. Ohsaka analyses the mode of action of hemorrhagic factors. These proteaseslcause breaks in the basement membrane of the vessels allowing erythrocytes to slide through and causing release of proteins and carbohydrates. There are other proteases with thrombin-like activity (thromboserpentine) found only in Pit-viper venoms which are not inhibited by antithrombins or by heparin. Other venom proteases hydrolyse coagulation factors or destroy platelets. Chapters by K. Hayashi et al., by Nahas et al. and by F. Kornalik et al. describe the isolation and properties of a number of venom proteases useful in coagulation research. Phospholipase A (phosphatide acyl hydrolase) is present in many venoms. The complete amino acid sequence of this enzyme isolated from Agkistrodin ha&s is reported by Y. Samejima et al. These phospholipases together with the phospholipase C excreted by various Clostridia (discussed in Section III ofVo1. 1) have proved useful in helping to locate the phospholipids of cell membranes. Nucleolytic enzymes especially phosphodiesterases of snake venoms are well known and are discussed in chapters by Laskowski et al. and by Schenberg et al. Interesting studies are reported by M.
94
Membrane proteins, where are you? The Enzymes of Biological branes Vol. I. Physical and Chemical Techniques
Mem-
edited by A. Martonosi, published by Plenum Press, New York, 1976. (257 pages)
Question: How do you write about a subject that does not exist? Answer: Either you write about the subject as you think it might exist in the future or else you write about something else. Unfortunately, it is the latter alternative that has generally been adopted in this volume. For a wide variety of fairly obvious technical reasons, virtually nothing is known about the molecular structure of membrane-bound proteins. This is contirmed by a reading of this book. Indeed, the book contains only one picture of a membrane protein : rhodopsin pictured as a rather lop-sided dumb-bell. The bulk of the reviews are concerned in fact with spectroscopic studies of lipids in model systems or in intact membranes, an interesting but much reviewed topic. In the first chapter Worthington reviews X-ray diffraction studies of membranes, and amply illustrates the difficulties associated with the correct choices of phase and correction factors. This leaves the general reader in something of a quandary. Thus the correct location for rhodopsin in the disc membrane has undoubtedly been determined by X-ray diffraction, undoubtedly because all possible locations have been proposed by one group of workers or another. The second chapter is a long review by Urry on nuclear magnetic resonance studies of the conformations of small peptides in organic solution, and discusses neither proteins nor membranes. This is then followed by two chapters on electron spin resonance by Gaffney, Lin, Vignais and Devaux. Overlap between the two chapters is considerable, both including discussion of the effects of solvent polarity and fluidity on spectra and concentrating on changes in membrane lipids. Next, Waggoner presents a very interesting review of fluorescence probe studies of membranes, but again discussion is of the membrane as a whole, and particularly its lipid component, rather than ofmembrane proteins. Tien and Mountz then convincingly demonstrate that nothing has been learnt about membrane proteins from studies with black lipid films. Discussion of membrane proteins really starts with the chapter by Tinberg and
Packer. They present a very stimulating review on chemical modification of membrane proteins, the technique which has given most information on three-dimensional structure. A technique withmuch promise, the use ofspecific antibodies, is discussed by Kyte. The two remaining chapters by Mavis and Gittler respectively deal with the effects of lipids on the activity of membrane bound proteins and the nature of lipid-protein interactions. All in all this book is rather disappointing, not as regards to any individual contribution but rather to the chosen topic for the volume. Despite much work and 257 pages the picture of a membrane protein that is left to haunt our dreams is of the lop-sided dumb-bell. A. G. LEE A. C. Lee is lecturer in the Department of Physiology and Biochemistry, University of Southampton, Southampton, U.K.
Toxic polypeptides Animal, Plant and Microbial Toxins : Vol. 1, Biochemistry ; Vol. 2, Chemistry, Pharmacology and Immunology edited by Akira Ohsaka, Kyozo Hayashi and Yoshio Sawai, published by Plenum Press, New York and London, 1976. Vol. I, $10.80 (approx. &5.-) (xxvi+.555 pages); Vol. 2, $10.80 (approx. &5.-) (xxv + 562 pages)
In these two volumes are published the proceedings of the Fourth International Symposium on Animal, Plant and Microbial Toxins held in Tokyo, Japan, 8-13 September, 1974. About half of all the chapters deal with the structure and pharmacological action of toxic polypeptides isolated from the venoms of snakes and scorpions. During the past few years more than 40 ‘neurotoxins’ and ‘cardiotoxins’ have been isolated from the venoms of Hydropidae and Elapidue snakes (sea snakes, cobras, kraits, etc.) and their primary structures have been determined. All of them, whether classified as neurotoxins or as cardiotoxins, have molecular weights between 7000 and 8000, contain either 4 or 5 intrachain disulfide bridges and show striking similarities in their amino acid sequence. The neurotoxins are of considerable interest to biologists because of their post-synaptic curare-like action and because they interact with and block cholinergic receptor sites. Progress on the chemical synthesis of toxic polypeptides is reported from two laboratories. Using the solid-phase techniques of Merrilield, N.
Izumya and his colleagues in Tokyo have synthesized a 62-amino acid polypeptide with about 6 % of the toxicity of cobra cardiotoxin. In the following chapter, V.T. Ivanov reports the use of classical techniques to synthesize 11 short polypeptides totalling 74 amino acids, which when joined together should yield r-bungarotoxin of the Taiwanian krait. Several chapters deal with similarities between toxins isolated from various species of scorpions and from cobra cardiotoxins. The toxic polypeptides isolated from both scorpion venoms and from snake venoms have molecular weights of about 7000, contain four intrachain disulfide linkages and unlike the typical snake ‘neurotoxins’, both act directly on the motor nerves to induce neuromuscular blockade and membrane depolarization. Snake venoms have long been known to contain many toxic enzymes of interest to the biochemist. First, I will deal with the proteases. Most snake bites cause hemorrhage at the site of injection into mammals. Mandelbaumetal. have isolated an hemorrhagic protease from Bothrops jararaca which cleaves four peptide bonds of the insulin B chain as follows : His-Leu (l& ll), Ala-Leu (1415), Trp-Leu (16-17) and Phe-Phe (24-25). The protease has almost no caseinolytic activity. Prescott et al. have studied proteases with similar specificity which they isolated from other species. In an interesting chapter, A. Ohsaka analyses the mode of action of hemorrhagic factors. These proteaseslcause breaks in the basement membrane of the vessels allowing erythrocytes to slide through and causing release of proteins and carbohydrates. There are other proteases with thrombin-like activity (thromboserpentine) found only in Pit-viper venoms which are not inhibited by antithrombins or by heparin. Other venom proteases hydrolyse coagulation factors or destroy platelets. Chapters by K. Hayashi et al., by Nahas et al. and by F. Kornalik et al. describe the isolation and properties of a number of venom proteases useful in coagulation research. Phospholipase A (phosphatide acyl hydrolase) is present in many venoms. The complete amino acid sequence of this enzyme isolated from Agkistrodin ha&s is reported by Y. Samejima et al. These phospholipases together with the phospholipase C excreted by various Clostridia (discussed in Section III ofVo1. 1) have proved useful in helping to locate the phospholipids of cell membranes. Nucleolytic enzymes especially phosphodiesterases of snake venoms are well known and are discussed in chapters by Laskowski et al. and by Schenberg et al. Interesting studies are reported by M.