Publisher Summary The chapter focuses on the new developments concerning yeast mannan structure and biosynthesis as they relate to the organization of the cell wall and the roles played by these glycoproteins. The mechanism of mannan biosynthesis is still in a rudimentary state, partly because of the insufficient knowledge concerning mannan structure and partly because of the inherent difficulties in working with such a complex macromolecule. Detailed information of Saccharomyces cerevisiae mannan can now be sketched and facilitates the planning of experiments on, and the interpretation of results from, biosynthetic studies. Moreover, the availability of mannan mutants with known polysaccharide structural alterations should prove advantageous. Studies of mannan biosynthesis have taken three general tacks. One approach has been directed toward an elucidation of the overall process of mannan formation and translocation within the cell using “pulsechase” techniques and autoradiography. The second approach has dealt with the formation and secretion of intact mannan molecules by yeast protoplasts and the inhibition of this process by compounds that prevent protein or polysaccharide synthesis. The third approach has investigations of the enzymic processes involved in mannan synthesis, using cell-free extracts and following incorporation of radioactive mannose into endogenous and exogenous acceptors. The chapter discusses the detailed structures of specific yeast mannans.

Structure and Biosynthesis of the Mannan Component of the Yeast Cell Envelope

The ultrastructure of yeast: Cell wall structure and formation

The cell wall is commonly regarded as an assemblage of polymers, mainly polysaccharides, that occurs outside the plasma membrane of cells of plants, fungi, and bacteria. Because of its rigidity it maintains the shape of the cell and offers resistance to unlimited influx of water into the cell. In addition it offers protection and, being the outermost cover of cells, often contains molecules involved in interaction between cells.

Fungal Cell Walls: A Survey

https://mmbr.asm.org/content/mmbr/43/2/117.full.pdf

Biosynthesis of cell walls of fungi.

Studies of ion channels have for long been dominated by the animalcentric, if not anthropocentric, view of physiology. The structures and activities of ion channels had, however, evolved long before the appearance of complex multicellular organisms on earth. The diversity of ion channels existing in cellular membranes of prokaryotes is a good example. Although at first it may appear as a paradox that most of what we know about the structure of eukaryotic ion channels is based on the structure of bacterial channels, this should not be surprising given the evolutionary relatedness of all living organisms and suitability of microbial cells for structural studies of biological macromolecules in a laboratory environment. Genome sequences of the human as well as various microbial, plant, and animal organisms unambiguously established the evolutionary links, whereas crystallographic studies of the structures of major types of ion channels published over the last decade clearly demonstrated the advantage of using microbes as experimental organisms. The purpose of this review is not only to provide an account of acquired knowledge on microbial ion channels but also to show that the study of microbes and their ion channels may also hold a key to solving unresolved molecular mysteries in the future.

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O Necas

Papers

Cell wall synthesis in yeast protoplasts.