Disulfides protein domains containing

The uPAR protein was initially purified from lysates of phorbol ester-stimulated U937 cells by affinity chromatography using diisopropyl fluoro-phosphates (DFP)-inactivated uPA [53, 54]. uPAR is anchored in the plasma membrane by a glycosylphosphatidylinositol (GPI) moiety and it consists of 283 amino acids in its processed form [55, 56]. The protein is composed of three domains and each domain contains 90 amino acids. The domains are connected by linker regions with a length of 15-20 amino acids [57, 58]. The disulfide bonds in the N-terminal domain I have been experimentally determined and the pattern of cysteine residues in the sequence has revealed... 

PE is a single-chain protein with a molecular mass of 66 kDa composed of three distinct domains (Fig. 2). In the PE protein, domain I (1-252) binds to the PE receptor on normal animal cells, which has been identified as the a2-macroglobulin receptor. Domain II (253-364) mediates translocation of domain III (400-613) into the cytosol. The translocation domain contains a proteolytic cleavage site within a disulfide loop, which, after proteolytic cleavage, leaves the cell-binding site (I) and translocation domain (II) bound to the catalytic/toxic site (III) by a disulfide bond (Fig. 2). Following reduction of this bond in the cytosol, the ADP-ribosylation activity of domain III inactivates elongation factor (EF2) and causes inhibition of protein synthesis and cell death. 

The 3D structure of hCp further resolved five disulfide bridges distributed evenly throughout the protein in domains 1-5. All five disulfides are near the bottom of a 3-barrel, and in two domains the Tl copper centers (TIB and TIC) are placed at the opposite end of the barrel. The only domain lacking a disulfide is domain 6, which contains TIA and the trinuclear copper centers. 

Chemokines, a sub-family of the cytokines. They are composed of a core domain containing two or three disulfide bonds in a flexible N-terminal domain whose truncation affects the potency of receptor activation. The chemokines are homologous 8- to 10-kDa proteins with 20 to 70% sequence homology. They are subdivided into at least four families based on the relative position of the Cys residues in the mature protein, although only the a- and -chemokines (both of which contain four Cys residues) have been well characterized. In the a-chemokines (CXC chemokines), the first two Cys residues are separated by a single amino acid residue (Cys-Xaa-Cys), whereas in the -chemokines (CC chemokines) the first two Cys residues are adjacent to each other (Cys-Cys). a-Chemokines are roughly 70 to 130 aa in size and are secreted with leader sequences of 20-25 aa which are cleaved before release. Besides the conserved Cys-Xaa-Cys motif near the N-terminus of the protein. 

FIGURE 16 Ribbon representation of irregular structures (a) High potential iron-sulfur protein coordinated to a 4Fe-4S cluster, (b) RAG1 DMA binding protein which contains representative examples of Zn-tinger domains, (c) Defensin as example of a membrane toxin stabilized by disulfide bonds, and (d) Chinese bird spider neurotoxin which contains a cystine knot. 

For larger proteins, stabilization occurs within each domain and also by interactions between domains. No quantitative data indicating the relative contribution of intra- and interdomain stabilizing interactions for any proteins are available. Certainly, this relative contribution depends upon the size, the interface interactions between domains, and the existence of disulfide bonds. Domains which contain disulfide linkages are certainly better stabilized. Such an evaluation would be interesting in order to predict the possibility of obtaining stable isolated domains from a multidomain protein. 

Figure 6.8 Schematic diagram of the enzyme DsbA which catalyzes disulfide bond formation and rearrangement. The enzyme is folded into two domains, one domain comprising five a helices (green) and a second domain which has a structure similar to the disulfide-containing redox protein thioredoxin (violet). The N-terminal extension (blue) is not present in thioredoxin. (Adapted from J.L. Martin et al.. Nature 365 464-468, 1993.)...

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