Proteins carbohydrate complexes with

All compounds have a precise and often highly specific function to fulfil, and in animals many of them are concerned also with the protection of the body against agents of disease. The problems of immunity and of enzyme systems involve the consideration of protein-carbohydrate complexes so that structural studies in the group now need to be undertaken seriously. 

This survival strategy may be more complex, however, as a number of studies 376, 377, 515, 516, 591-593, 744, 832, 891) have indicated that pseudophyllidean and cyclophyllidean cestodes produce their own protease inhibitors which can inactivate trypsin and chymotrypsin in vitro. Such protease inhibitors are also produced by nematodes and they appear to be proteins or protein-carbohydrate complexes 592). Precise chemical characterisation of these protease inhibitors has not yet been achieved in cestodes, although the active molecule from the strobilocercus of T. taeniaeformis has been shown to be a polypeptide taeniaestatin) with an Mt of 19 500 under reducing conditions 832). The effectiveness of this molecule at inhibiting chymotrypsin in vitro is illustrated in Fig. 4.1. The mechanism whereby this and... 

The ability of water to act as both donor and acceptor of hydrogen bonds makes it an excellent mediator in protein-carbohydrate complexes. Results of numerous X-ray crystallographic studies of protein-carbohydrate complexes attest to the pervasiveness of water-mediated hydrogen bonds in protein-carbohydrate interactions. Lectin-bound water molecules are proposed to act as an extension of the protein surface itself [1]. This idea is supported by the fact that water molecules occupy conserved sites in the structures of related lectins [24]. In addition, water molecules can mediate similar hydrogen bonding interactions in the complexes of different proteins with a specific carbohydrate ligand or in complexes of the same lectin with different saccharide ligands [1]. 

Wheat gluten is a protein carbohydrate complex of which proteins are the major component. Two main fractions are present gliadin, which is soluble in neutral 70% ethanol, made of single chain polypeptides with an average molecular... 

Fig. 11. UDA-VI forms a 2 2 protein-sugar complex with (GlcNAc)3. The mode of sugar binding for UDA VI differs partially from that of UDA I (Fig. 12). One (GlcNAc)3 trisaccharide is sandwiched between two different UDA-VI molecules, as shown in the figure. This positioning accounts for extensive aromatic-carbohydrate contacts (pdb codes, lEHD, lEHH, lEIS, lENM).

Brenda Lauterbach and Professor Peter Reilly, Department of Chemical Engineering, Iowa State University, assisted with the analysis of the protein-carbohydrate complexes and Ms Lauterbach read the manuscript. Dr. Alexander Lambert, Southern Regional Research Center, and Mary An Godshall, Sugar... 

Higher Oligosacdiarides and C-Glyco es. - Following the previous section, not only di-, but tri- and tetrasaccharide complexes of rainbow trout lysozyme have been characterized by X-ray analysis. The orientation of the (a 1- 6) mannosyl arm of a heptasaccharide and hexasacchatide (and disaccharide fragments) has been studied by molecular dynamics simulations and compared with protein-carbohydrate complex crystal structures. ... 

Examples from other groups include gas-phase thermal dissociation experiments, implemented with blackbody infrared radiative dissociation (BIRD) and FT-ICR MS on a series of protein-carbohydrate complexes, and the detection of fusion peptide-phospholipid noncovalent interactions using nano-ESI FTICR-MS. An interesting example of protein-DNA interaction smdied by ESI-MS is the trp repressor-DNA operator complex. Escherichia coli trp apo-repressor (TrpR), a homodimer, is a DNA-binding protein that binds to two molecules of co-repressor L-tryptophan to form a holorepressor complex at higher salt concentrations. The mass spectrum of noncovalent... 

Figure 3. Schematic representation of the transfer NOESY (trNOESY) experiment. Ligands have to sample the binding site of the protein (shown in red) often enough during the mixing time in order to generate a transfer of NOEs. It follows that dissociation of the protein-carbohydrate complex must be fast on the relaxation time scale. With mixing times tn, usually being 50-300 ms for trNOESY experiments, dissociation rates of ca. 50-100 Hz are sufficient.

Mollusks are not the only invertebrates to produce bioadhesives the same is true for sedentary Polychaetes such as Phragmatopoma califomica, which live in tubes impregnated with grains of sand (see Chapter 21), as well as for most sea cucumbers that use their Cuvierian tubules to defend themselves against predators (Jensen and Morse, 1988 Waite, Jensen, and Morse, 1992 Deming, 1999 Stewart et al, 2004 Flammang, 2003). Lastly, bioadhesives produced by the sea urchin Paracentrotus lividus to inhabit wave-swept shores are constituted by protein-carbohydrate complexes and are devoid of dopa (Santos et al, 2009). 

Some six hundred structures of naturally occurring carbogenic molecules appe on the pages which follow, together with the name of each compound and references to the original literature of successful chemical synthesis. Thus, Part Three of this book is effectively a key to the literature of chemical synthesis as applied to the complex molecules of nature. The survey does not include oligomeric or polymeric structures, such as peptides, proteins, carbohydrates and polynucleotides, which fall outside the scope of this book because they can be assembled by repetitive procedures. 

Coelenterates and Echinoderms. Coelenterate and echinoderm toxins range from small molecular weight amines, to sterols, to large complex carbohydrate chains, to proteins of over 100,000 daltons. Molecular size sometimes reflects taxonomy, e.g., sea anemones (Actiniaria) all possess toxic polypeptides varying in size from 3,000 to 10,000 daltons while jellyfish contain toxic proteins (ca. 100,000 daltons). Carotenoids have been isolated from Asterias species (starfish), Echinoidea (sea urchins), and Anthozoans such as Actiniaria (sea anemones) and the corals. These are sometimes complexed with sterols (J5). 

Allen et al. (2007) produced puffed snack foods with com starch and pregelatinized waxy starch, WPC and instantized WPC, and protein concentrations of 16%, 32%, and 40% and showed that the air cell size, extru-date expansion ratio, and water solubility index decreased proportionally as protein and com starch levels increased. Protein concentration significantly affected total soluble protein, water absorption index, and water-soluble carbohydrate. A covalent complex between amylase and protein formed in the presence of cornstarch, but protein-protein interactions appeared with the presence of low levels of pregelatinized waxy starch. 

The general types of protein-protein interactions that occur in cells include receptor-ligand, enzyme-substrate, multimeric complex formations, structural scaffolds, and chaperones. However, proteins interact with more targets than just other proteins. Protein interactions can include protein-protein or protein-peptide, protein-DNA/RNA or protein-nucleic acid, protein-glycan or protein-carbohydrate, protein-lipid or protein-membrane, and protein-small molecule or protein-ligand. It is likely that every molecule within a cell has some kind of specific interaction with a protein. 

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