Molecular Mechanisms In Visual Transduction

Molecular mechanisms in visual transduction is presently one of the most intensely studied areas in the field of signal transduction research in biological cells. Because the sense of vision plays a primary role in animal biology, and thus has been subject to long evolutionary development, the molecular and cellular mechanisms underlying vision have a high degree of sensitivity and versatility. The aims of visual transduction research are first to determine which molecules participate, and then to understand how they act in concert to produce the exquisite electrical responses of the photoreceptor cells. Since the 1940s [1] we have known that rod vision begins with the capture of a quantum of energy, a photon, by a visual pigment molecule, rhodopsin. As the function of photon absorption is to convert the visual pigment molecule into a G-protein activating state, the structural details of the visual pigments must be explained from the perspective of their role in activating their specific G-proteins. Thus, Chapters 1-3 of this Handbook extensively cover the physico-chemical molecular characteristics of the vertebrate rhodopsins. Following photoconversion and G-protein activation, the phototransduction cascade leads to modifications of the population of closed and open ion channels in the photoreceptor plasma membrane, and thereby to the electrical response. The nature of the channels of vertebrate photoreceptors is examined in Chapter 4, and Chapter 5 integrates the present body of knowledge of the activation steps in the cascade into a quantitative framework. Once the phototransduction cascade is activated, it must be subsequently silenced. The various molecular mechanisms participating in inactivation are treated in Chapters 1-4 and especially Chapter 5. Molecular biology is now an indispensable tool in signal transduction studies. Numerous vertebrate (Chapter 6) and invertebrate (Chapter 7) visual pigments have been characterized and cloned. The genetics and evolutionary aspects of this great subfamily of G-protein activating receptors are intriguing as they present a natural probe for the intimate relationship between structure and function of the visual pigments. Understanding the spectral characteristics from the molecular composition can be expected to

Brings together key new results of interdisciplinary collaborations among various research fields on rhodopsin including the photoreceptive mechanism of rhodopsins, the molecular mechanism of the visual transduction process, visual processes in the retina and other transduction processes in the retina and brain. The structures of the rhodopsin molecule are studied in the fields of protein chemistry, molecular biology, organic chemistry and structural biology; the ultra fast reactions of the retinal protein are studied in physics, biophysics, physical chemistry, organic chemistry and photobiology; the phototransduction in retinal proteins and visual cells are studied in biophysics, biochemistry, biophysical chemistry and photobiology; and the localization in the tissues is studied in anatomy and histochemistry. The diversity of visual systems in various animals is studied in zoology and comparative biochemistry.

This book reveals not only how the eye evolved into an organ of vision, but also describes how molecular mechanisms of key molecules operate in the phototransduction cascade. In this groundbreaking text, experts also explain mechanisms for sensing radiation outside of the visible wavelengths. Comprehensive and penetrating, the book brings together the mechanisms of the visual transduction cascade and is an invaluable text for everyone conducting research in the visual system.

very important, especially the comparison of vertebrate and invertebrate transduction mechanisms. The workshop was very successful and the outcome of the discussions proved it worth the effort. To no small extent has that success been made possible by Dr. Silke Bernhard who with a combination of authority and charm together with her extremely efficient and dedicated staff organized this workshop, providing the conditions and framework for a scientific debate of outstanding quality in a friendly and pleasant atmosphere. The great majority of participants were also very committed to making this workshop successful. Besides the reports of the four discussion groups, this publication contains the background papers which were revised by the authors partly as a result of suggestions of some participants. I hope this book will give a fair overview of the state of our knowledge of research in visual transduction. It was a pleasure to edit, especially because of the friendly and very efficient commitment of K. Geue, J. Lupp, and A. Eckert and the cooperativeness of most of the contributors. Particularly I would like to acknowledge gratefully the extensive efforts and patience of the four rapporteurs, M.L. Applebury, W.H. Miller, W.G. Owen, and E.N. Pugh, Jr., in compiling, writing, and revising the group reports. REFERENCES (1) Altman, J. 1985. Sensory transduction, new visions in photoreception. Nature 313: 264-265. (2) Hagins, W.A. 1972. The visual process: Excitatory mechanisms in the primary receptor cells. Ann. Rev. Biophys. Bioeng. 1: 131-158.

EJB Reviews 1989 offer the collection of all reviews published in the European Journal of Biochemistry in one handy volume. This series of review articles by leading scientists covers emerging and rapidly growing fields of research in fundamental as well as in applied areas of biochemistry, such as medicine, biotechnology, agriculture and nutrition. Novel methodological and technological approaches which stimulate biochemical research are also included. All authors review their field in a very critical, selective, evaluative manner, with emphasis on interdisciplinary aspects wherever possible.

In the twenty-first century, we are just beginning to understand more clearly the enormous diversity and complexity of signaling processes in the retina. Integrating advances in the biochemistry, cell biology, physiology, and physics of phototransduction, Signal Transduction in the Retina presents the methodologies and experimental approache

Understanding the mechanisms that underlie brain activity and function remains one of the major frontiers of biology. All the processes of how we co-ordinate our movements, sense our surroundings, react to stimuli and learn and retain information rely on complicated networks of neurons thatcommunicate with each other and their targets. This fast and accurate intercellular signalling most occurs at synapses, specialized processes of neurons that release chemical signals, called neurotransmitters. Neurotransmitters: Frontiers in Molecular Biology will provide the reader withextensive background information on neurotransmitter release. It takes a multidisciplinary approach, but does not assume previous knowledge having basic introductions to most topics. Topics however are covered in enough detail to be of interest to experts in the field. Throughout, emphasis is placedon the rationale by which proteins are assigned specific functions rather than just providing facts about function. The first chapter provides an introduction to the basic features and properties of the synapse and is followed by a chapter detailing several important techniques used to elucidatevarious aspects of release. Chapters 3 describes many of the biochemical approaches used to identify proteins involved in neurotransmitter release and then chapters 4 and 5 focus on more specific aspects of synaptic transmission: the proteins that transport neurotransmitters and the role ofphosphlipids in the process. The next five chapters concentrate on approaches to unravel the function of many proteins in vivo by using toxins, giant squid axons, C. elegans, Drosophila, and mice. The final chapter summarizes current knowledge on endocytosis and recycling. Knowledge of themolecular mechanisms underlying neurotransmitter release has expanded tremendously over the last 10 years. Many of the proteins involved have been isolated, but their roles have yet to be determined. These discoveries will be a major challenge and it is therefore the major aim of this book not onlyto provide information but also to generate excitement.