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Disulphide bonds, proteins

Bovine heart valve collagen has been solubilized by digestion with pepsin followed by extraction with dithiothreitol under non-denaturing conditions. It is implied that disulphide-bonded proteins may be partly responsible for the insolubility of this collagen. [Pg.314]

Martin, J.E., Bardwell, J.C.A., Kuriyan, J. Crystal structure of the DsbA protein required for disulphide bond formation in vivo. Nature 365 464-468, 1993. [Pg.119]

Figure 3.4 Transmembrane topology of a 7-TM domain G-protein receptor such as the P-adrenoceptor. Agonist binding is predicted to be within the transmembrane domains. The extracellular structure is stabilised by the disulphide bond joining the first and second extracellular loop. The third intracellular loop is the main site of G-protein interaction while the third intracellular loop and carboxy tail are targets for phosphorylation by kinases responsible for initiating receptor desensitisation... Figure 3.4 Transmembrane topology of a 7-TM domain G-protein receptor such as the P-adrenoceptor. Agonist binding is predicted to be within the transmembrane domains. The extracellular structure is stabilised by the disulphide bond joining the first and second extracellular loop. The third intracellular loop is the main site of G-protein interaction while the third intracellular loop and carboxy tail are targets for phosphorylation by kinases responsible for initiating receptor desensitisation...
NA isolation and molecular characterization will be important to define the origin and functions of these proteins. At this time, infected cell nuclei offer the only source of these proteins, and NA have proved resistant to classic nuclear extraction methods (Yao and Jasmer, 1998). NA can be solubilized under conditions that co-extract nuclear lamins a/c and b (4 M urea, pH 8.0). Despite these similar physical properties, NA do not co-localize with lamins in the nucleoskeleton. However, both disulphide bonds and ionic interactions appear to contribute to nuclear complexes containing NA. In addition, NA can be cross-linked within host nuclei with protein cross-linking reagents. The foregoing properties represent current information available for the development of strategies to isolate and characterize these proteins and to investigate host proteins with which NA interact. [Pg.139]

Figure 11.5 Globular proteins. The folding of a polypeptide chain in a globular form is stabilized by hydrophobic interactions and some covalent bonding, particularly the disulphide bond between cysteine residues. The polypeptide chain shows some sections which are regular and helical in nature and other sections, particularly at bends and folds, where the conformation of the chain is distorted. Figure 11.5 Globular proteins. The folding of a polypeptide chain in a globular form is stabilized by hydrophobic interactions and some covalent bonding, particularly the disulphide bond between cysteine residues. The polypeptide chain shows some sections which are regular and helical in nature and other sections, particularly at bends and folds, where the conformation of the chain is distorted.
The nature of the amino acid residues is of prime importance in the development and maintenance of protein structure. Polypeptide chains composed of simple aliphatic amino acids tend to form helices more readily than do those involving many different amino acids. Sections of a polypeptide chain which are mainly non-polar and hydrophobic tend to be buried in the interior of the molecule away from the interface with water, whereas the polar amino acid residues usually lie on the exterior of a globular protein. The folded polypeptide chain is further stabilized by the presence of disulphide bonds, which are produced by the oxidation of two cysteine residues. Such covalent bonds are extremely important in maintaining protein structure, both internally in the globular proteins and externally in the bonding between adjacent chains in the fibrous proteins. [Pg.385]

Brazzein is another small sweet-tasting protein whose solution structure has been recently solved by NMR. Brazzein tastes 2000 times sweeter than sucrose on a weight basis and is exceptionally thermostable. As indicated by NMR, the structure of this 54 residue, single-chain polypeptide does not change between 32 and 82 °C and retains its sweetness after incubation at 98 °C for two hours.Brazzein contains one a-helix and three strands of antiparallel jd-sheet stabilized by four intramolecular disulphide bonds. It has been proposed that the disulphide bonds could be responsible for the thermostability of brazzein by forming a compact structure at the tertiary level.The structure of brazzein does not resemble that of the other two sweet proteins with known structures, monellin and thaumatin, whereas sequence alignment and structural prediction indicate that brazzein shares the fold of a newly identified family of serine proteinase inhibitors. [Pg.149]

Creighton, T. E. (1986). Disulphide bonds as probes of protein folding pathways. Method Enzymol. 131,83-106. [Pg.21]

HSA is a 585 amino acid, 65.5 kDa polypeptide. It is one of the few plasma proteins that is unglycosylated. A prominent feature is the presence of 17 disulphide bonds, which helps stabilize the molecule s 3-D structure. HSA is synthesized and secreted from the liver, and its gene is present on human chromosome 4. [Pg.355]

The method described here is based on two reactions first, the reduction of the disulphide bond between Hey and other thiols or the cysteine residue of proteins by the reducing compound tri-n-butylphosphine (Fig. 2.2.2a) followed by the reaction of Hey and other thiols with the flourogenic thiol-specific reagent ammonium... [Pg.94]

SO is capable of oxidizing reduced ribonuclease and restoring enzymic activity, suggesting that its physiological role may be the non-random formation of protein disulphide bonds, e.g. during protein biosynthesis. [Pg.249]

SOD, isolated from bovine erythrocytes, is a blue-green protein due to the presence of copper, removal of which by treatment with EDTA results in loss of activity, which is restored by adding Cu2+ it also contains Zn2+, which does not appear to be at the active site. The enzyme, which is very stable in 9 M urea at neutral pH, consists of two identical subunits of molecular weight 16kDa held together by one or more disulphide bonds. The amino acid sequence has been established. [Pg.250]

Reductants provide a means to fully denature proteins within the sample and aid solubilization. To fully break disulphide bonds,... [Pg.331]


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