Sulfhydryl groups and disulfide

Krieglstein, K.G., DasGupta, B.R. and Henschen, A.H., Covalent structure of botulinum neurotoxin type-A-location of sulfhydryl groups, and disulfide... 

Sulfhydryl groups and disulfide bonds, and their interrelationships, are important groups affecting the properties of the majority of proteins and are under continuous study by protein chemists. Indeed, the reduction of disulfides to form sulf-hydryls, and the reoxidation of these to re-form the correct pairings (Figure 11), are intimately related to the entire subject of protein conformation and conformational changes (27). 

Heating of meat is accompanied by changes in appearance, taste, texture, smell and nutritional value (7). The sulfhydryl groups and disulfide bonds which are moieties of cysteine and cystine contribute to these qualities in meat. Sulfur-containing compounds including disulfides are often found in foodstuffs and usually contribute to the overall aroma of such food because of their low threshold values (2). Sulfur compounds are major contributors to the flavor of cooked products (J). Furthermore, destruction of labile amino acids during heat processing operations may have detrimental effects on nutritional value of such products. 

The sulfhydryl groups and disulfide bonds play important roles in the functional and structural properties of heat-processed meat. During thermal processing, disulfide cross-linking of protein molecules may occur. This has been reported in fish, meat, squid, and seal (4-7). Sulfhydryl-dependent gelation of hen egg lysozyme at SO C has been demonstrated. These proteins had several intramolecular disulfide bonds with a good correlation between... 

In the present study, we assessed the effect of heating and aqueous washing of mechanically separated seal meat (MSSM) and mechanically separated chicken meat (MSCM) on the content of sulfhydryl groups and disulfide bonds in their proteins. An attempt was made to correlate the content of sulfhydryl groups with changes in the solubility and thermal coagulation of mechanically separated meat proteins. 

Table I. Sulfhydryl groups and disulfide bonds in MSSM and MSCM...

For CNBE, modification of the purified CNBE by DEPC shows that 1 mole of histidine residue existed in the active site of the enzyme. Modification by NBS shows that tryptophan residues existed in the active site and there is at least 1 mole of tryptophan residue in the substrate binding site. Results of modification by Ch-T and EDAC indicate that methionine residues and carboxyl groups were essential groups of the purified enzyme. In addition, hydroxyl groups, arginine residues, tyrosine residues, sulfhydryl groups, and disulfide bonds were not essential groups of the purified enzyme [100],... 

Ravizzini RA, Andreo CS and Vallejos RH (1980) Sulfhydryl groups in photosynthetic energy conservation VI. Subunit distribution of sulfhydryl groups and disulfide bonds in chloroplast coupling factor and ATPase activity, Biochim.Biophys.Acta 591, 135-141. 

Some proteins contain covalent disulfide (S— S) bonds that link the sulfhydryl groups of cysteinyl residues. Formation of disulfide bonds involves oxidation of the cysteinyl sulfhydryl groups and requires oxygen. Intrapolypeptide disulfide bonds further enhance the stability of the folded conformation of a peptide, while interpolypeptide disulfide bonds stabilize the quaternary structure of certain oligomeric proteins. 

Purify the thiolated protein from unreacted Traut s reagent by gel filtration using your buffer of choice (i.e., 20mM sodium phosphate, 0.15M NaCl, ImM EDTA, pH 7.2). The addition of EDTA to this buffer helps to prevent oxidation of the sulfhydryl groups and the resultant disulfide formation. After purification, use the thiolated protein immediately... 

Nuclease is composed of 149 amino acid residues, and contains neither sulfhydryl groups nor disulfide bonds (20, 25, 26). Figure 1 shows the amino acid sequence of nuclease isolated from Staphylococcus aureus, strain V8 (20, 25-27). Physical measurements of the molecular weight of nuclease from strain V8 as well as from strain Foggi are consistent with this sequence (28). 

There are four disulfide bonds in ribonuclease. If these are reduced to their component sulfhydryl groups and allowed to reoxidize, how many different combinations of disulfide bonds are possible ... 

Oxidations of sulfhydryl groups to disulfides, of alcohols to aldehydes and ketones, and of aldehydes to carboxylic acids frequently occur. 

If, based on the gene sequence for the desired product, cysteine residues are expected, the number and positions of any free sulfhydryl groups and/or disulfide bridges should be determined, to the extent possible. Peptide mapping (under reducing and nonreducing conditions), MS, or other appropriate techniques may be useful for this evaluation. 

The sequence of stem bromelain contains one sulfhydryl group and three intrapeptide disulfide bonds [45]. The homology between stem bromelain and members of the papain family was first demonstrated by alignment of cyanogen bromide fragments of stem bromelain with the sequence of papain [48,54] and by studying the immunological cross-reactions between different cysteine proteinases [55-57]. 

Tsen, C.C. 1966. A note on effects of pH on sulfhydryl groups and rheological properties of dough and its implication with the sulfhydryl-disulfide interchange. Cereal Chem. 43, 456-460. 

M sodium phosphate, 0.15 M NaCl, pH 7.5, containing 10 mM EDTA. The presence of EDTA in this buffer helps to prevent oxidation of the sulfhydryl groups and resultant disulfide formation. The degree of —SH modification in the purified protein may be determined using the Ellman s assay (Chapter 1, Section 4.1). 

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