Disulfide bonds proteins lacking

The dehydron/disulfide balance relation clearly identifies proteins with excess (Y > 5X + 20) or lack (Y < 5X + 20) of structural deficiencies, with the former likely to be more favorably denatured than the latter under equivalent redox and denatura-tion conditions. To test this prediction, thermodynamic data on thermal denaturation (Table 2.2) were obtained for an exhaustive set of proteins for which structural information was also available [7], Thus, the thermal denaturation free energy change, AG, under reducing conditions and comparable temperatures [11], was obtained for monomeric uncomplexed PDB-reported proteins with disulfide bonds and lacking prosthetic groups or ion coordination. A significant anticorrelation was found... 

Mature human albumin consists of one polypeptide chain of 585 amino acids and contains 17 disulfide bonds. By the use of proteases, albumin can be subdivided into three domains, which have different functions. Albumin has an ellipsoidal shape, which means that it does not increase the viscosity of the plasma as much as an elongated molecule such as fibrinogen does. Because of its relatively low molecular mass (about 69 kDa) and high concentration, albumin is thought to be responsible for 75-80% of the osmotic pressure of human plasma. Electrophoretic smdies have shown that the plasma of certain humans lacks albumin. These subjects are said to exhibit analbuminemia. One cause of this condition is a mutation that affects spUcing. Subjects with analbuminemia show only moderate edema, despite the fact that albumin is the major determinant of plasma osmotic pressure. It is thought that the amounts of the other plasma proteins increase and compensate for the lack of albumin. 

Spectra, but, in general, leaves the copper site the most exposed of the four cupredoxins. The sequence of Cbp is quite similar to that of stella-cyanin. Stellacyanin is a plant protein, also of unknown function, having visible spectra characteristic of type I copper, but lacking the methionine ligand found in all other type I proteins. A disulfide bond has been suggested as a potential copper ligand in stellacyanin the Cbp has both a methionine and the disulfide, so that prior to the structure determina-... 

The system of intraglobular residue-residue contacts of a protein of N residues may be represented as an N x N matrix of the carbon-alphas, whose elements are ones (contact) or zeros (lack of contact). Any reasonable definition of contact provides ones in the positions (i, i + l)that correspond to a peptide bond between two adjacent residues in the sequence. The same is true for the residues corresponding to the pair of cysteines forming a disulfide bond (these data may not be available as input and may be used as a test of correct prediction). This set of contacts describes the sequential covalent topology and is a constant part of the contact matrix which does not depend on the spatial structure of the polypeptide chain however, any additional information on existing intraglobular contacts (e.g., from NMR data or disulfide linkage) can easily be introduced in the constant part of the contact matrix A ... 

In some proteins, the linear polypeptide chain is cross-linked. The most common cross-links are disulfide bonds, formed by the oxidation of a pair of cysteine residues (Figure 3.21). The resulting unit of linked cysteines is called cystine. Extracellular proteins often have several disulfide bonds, whereas intracellular proteins usually lack them. Rarely, nondisulfide cross-links derived from other side chains are present in some proteins. For example, collagen fibers in connective tissue are strengthened in this way, as are fibrin blood clots. 

Cysteine and cystine. Most cytosolic proteins lack disulfide bonds, whereas extracellular proteins usually contain them. Why ... 

This method gives high yields, both for the enzyme (80%) and for the antibody (60%), although 25% may be present in the form of aggregates, some of which may have pre-existed. Conjugation with MBS, however, is somewhat less efficient than with CHM-NHS for POase, APase, or GOase. For proteins which lack sulfhydryl groups, thiolation or reduction of disulfide bonds is required (Yoshi-take et al., 1982). 

---