Transport Of Molecules Across Microbial Membranes

This volume details the transport of molecules, large and small, across the membranes of prokaryotic and eukaryotic microbial cells. An international group of contributors unify a diverse range of phenomena with the discussion of the signal peptides that target proteins to particular destinations, and the role of chaperonins. Topics covered include secretion of proteins out of the bacterial cell by Type I, II, and III mechanisms, including the newly recognized bacterial signal recognition pathway in Type II; passage across internal membranes of eukaryotic proteins, whether destined for secretion or en route to internal organelles such as chloroplasts and peroxisomes; how bacteria obtain energy required for solute uptake; the role of phosphorylation and evolutionary relationships of the proteins involved; and efflux pumps for toxic substances in bacterial, animal, and plant cells.

Transport of molecules across the cell membrane is a fundamental process of all living organisms. It is essential for understanding growth, development, nutrition as well as uptake and excretion of exogenous or synthesized molecules. Microbes respresent general and basic functional systems where many transport processes have been studied on a molecular basis. Knowledge of the microbial transport processes will provide new perspectives to treatments by inhibitors, drugs, antibiotics, vitamins, growth promotion compounds, activators and toxic compunds of various kinds.

This book provides a comprehensive overview of the basic principles, concepts, techniques and latest advances in the field of biomembranes and membrane-associated processes. With new emerging technologies and bioinformatics tools, this is a promising area for future study and research. The book discusses the composition, fluidity and dynamic nature of phospholipid bilayers, which vary with cell/organelle type and function. It describes the various types of transport proteins that facilitate the transport of polar and nonpolar molecules across the membrane actively or passively via ion-channels or through porins. It also explores the many cellular functions membranes participate in: (1) energy transduction, which includes the electron transport chain in inner membrane of mitochondria and bacterial cytoplasmic membrane and photosynthetic electron transport in thylakoid membranes in chloroplast and photosynthetic bacterial membranes; (2) cell–cell communication involving various signal transduction pathways triggered by activated membrane receptors; (3) cell–cell interactions involving various types of adhesion and receptor proteins; (4) nerve transmission involving opening and closing of voltage gated ionic channels; and (5) intracellular transport involving the processes of endocytosis, exocytosis, vesicular transport of solutes between intracellular compartments, membrane fusion and membrane biogenesis.

One property common to all cells is transport. Molecules and ions must enter and leave cells by crossing membranes in a controlled manner. The process may take any of several forms: simple diffusion, carrier-mediated diffusion, active transport, or group translocation. There is more than one way to measure each. Transport kinetics, with particular reference to the red blood cell, were discussed in a previous volume. Three chapters deal with the general subject of transport in this volume. Maloney, Kashket, and Wilson summarize the appropriate methodology for studying metabolite and ion transport in bacteria, and Kimmich describes the relevant method ology for the isolated intestinal epithelial cell. The methods described in these two chapters have general application to transport studies in single cells from any source. The approach described in these two complementary articles is extended in the chapter by Hochstadt and her collaborators on the use of isolated membranes from bacterial and mammalian cells for the study of trans port phenomena. If one can prepare a suitable plasma membrane fraction (sealed, impermeable vesicles with the necessary transport components intact), it becomes possible to separate the events of transport from any subsequent metabolism that may occur in the cell. Isolated membrane vesicles are relatively easy to obtain from bacteria, and they are com paratively well studied. Work with similar preparations from cultured mammalian cells is just beginning but has much promise.

An Introduction to Biological Membranes: From Bilayers to Rafts covers many aspects of membrane structure/function that bridges membrane biophysics and cell biology. Offering cohesive, foundational information, this publication is valuable for advanced undergraduate students, graduate students and membranologists who seek a broad overview of membrane science. Brings together different facets of membrane research in a universally understandable manner Emphasis on the historical development of the field Topics include membrane sugars, membrane models, membrane isolation methods, and membrane transport.