Binding protein-polysaccharide

Several other properties of selected dietary fibers may influence the bioavailability of calcium directly or indirectly. Those fibers which have cation exchange capabilities such as acid polysaccharides due to free carboxyl groups on the sugar residues may bind minerals such as calcium (3,17,33,36). Loss of calcium binding protein as a result of mucosa injury caused by the feeding of some kinds of dietary fiber was credited as being the partial cause of decreased calcium absorption in everted, rat gut sac studies by Oku et al. (16). 

Heparin has been found to bind a large number of proteins (Table 3). The biological activity of heparin and related polysaccharides is usually ascribed to their interaction with heparin-binding proteins. These proteins can be classified into classes including (1) enzymes, (2) protease inhibitors, (3) lipoproteins, (4) growth factors, (5) chemokines, (6) selectins, (7) extracellular matrix proteins, (8) receptor proteins, (9) viral coat proteins, (10) nuclear proteins, and (11) other proteins (1). Many heparin-binding proteins are enzymes and enzyme inhibitors. For example, proteases in the coagulation cascade, such as factors Ha, IXa, Xa, Xlla, and Villa, are heparin-... 

Macromolecules such as proteins, polysaccharides, nucleic acids differ only in their physicochemical properties within the individual groups and their isolation on the basis of these differences is therefore difficult and time consuming. Considerable decreases may occur during their isolation procedure due to denaturation, cleavage, enz3rmatic hydrolysis, etc. The ability to bind other molecules reversibly is one of the most important properties of these molecules. The formation of specific and reversible complexes of biological macromolecules can serve as basis of their separation, purification and analysis by the affinity chromatography [6]. 

Woodward, C., Davidson, E. A. Structure-function relationships of protein polysaccharide complexes specific ion-binding properties. Proc. Nat. Acad. Sci. (Wash.) 60, 201 (1968)... 

Smith, Q. T., Lindenbaum, A. Composition and calcium-binding of protein-polysaccharides of calf nasal septum and scapula. Calc. Tiss. Res. 7, 290 (1971)... 

At least three other families of plasma membrane proteins are also involved in surface adhesion (Fig. 11-22). Cadherins undergo homophilic ( with same kind ) interactions with identical cadherins in an adjacent cell. Immunoglobulin-like proteins can undergo either homophilic interactions with their identical counterparts on another cell or heterophilic interactions with an integrin on a neighboring cell. Selectins have extracellular domains that, in the presence of Ca2+, bind specific polysaccharides on the surface of an adjacent cell. Selectins are present primarily in the various types of blood cells and in the endothelial cells that line blood vessels (see Fig. 7-33). They are an essential part of the blood-clotting process. 

The covalent attachment of arabinose and galactose to the hydroxy-L-proline-rich protein of primary cell-walls is now generally accepted,228230 but the evidence available suggests that the glycoprotein is not covalently attached to any of the other cell-wall polymers, This, of course, does not preclude the possibility of the existence of strong, non-covalent forces binding protein to wall polysaccharides.228,230... 

The controlled deposition of calcium salts is essential for the development of extracellular structures such as bones, teeth and shell. The process begins with uptake of calcium in the intestine, followed by transport, and then the laying down of structures. A complex system is necessary for the control of all these stages, and involves, for example, vitamin D, parathyroid hormone, calcium-binding proteins for transport, and a range of other proteins and polysaccharides for ordered deposition. Precipitation of calcium salts in the incorrect location can result in stone formation, osteoarthritis, cataracts and arterial disorders. 

In addition to their role in primary stabilization related to viscosity increase, some hydrocolloids (particularly carrageenan) are traditionally used as secondary stabilizers. Many of the primary stabilizing hydrocolloids, including locust bean gum and carboxy methyl cellulose induce precipitation of the milk proteins in the mix. This phenomenon in ice cream mix is known as wheying-off, and may be due to direct protein-polysaccharide binding and/or protein-polysaccharide incompatibility in the water phase40. The latter phenomenon may be due to decreased solvent quality due to the competition between protein and polysaccharide for solubilisation. 

CONTENTS Introduction to the Series An Editor s Foreword, Albert Padwa. Preface, C. Allen Bush. Raman Spectroscopy of Nucleic Acids and Their Complexes. George J. Thomas, Jr. and Masamichi Tsuboi. Oligosaccharide Conformation in Pro-tein/Carbohydrate Complexes, Anne Imberty, Yves Bourne, Christian Cambillau and Serge Perez. Geometric Requirements of Proton Transfers, Steve Scheiner. Structural Dynamics of Calcium-Binding Proteins, Robert F. Steiner. Determination of the Chemical Structure of Complex Polysaccharides, C. Abeygunawardana and C. Allen Bush. Index. 

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