Disulphide binding

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...

In the family of cation pumps, only the Na,K-ATPase and H,K-ATPase possess a p subunit glycoprotein (Table II), while the Ca-ATPase and H-ATPase only consist of an a subunit with close to 1 000 amino acid residues. It is tempting to propose that the p subunit should be involved in binding and transport of potassium, but the functional domains related to catalysis in Na,K-ATPase seem to be contributed exclusively by the a subunit. The functional role of the P subunit is related to biosynthesis, intracellular transport and cell-cell contacts. The P subunit is required for assembly of the aj8 unit in the endoplasmic reticulum [20]. Association with a j8 subunit is required for maturation of the a subunit and for intracellular transport of the xP unit to the plasma membrane. In the jSl-subunit isoform, three disulphide... 

Figure 2. Correspondence of the calculated backbone trace with that of the reported backbone for BP2 [19], As well, the calculated disulphide bridges are included to illustrate the important role they play in protein structure, binding certain regions together. 

Stenham, D.R., Campbell, J.D., Sansom, M.S.P., Higgins, C.F., Kerr, I.D. and Linton, K.J. (2003) An atomic detail model for the human ATP binding cassette transporter P-glycoprotein derived from disulphide cross-linking and homology modelling. FASEB Journal, 17, 2287-2289. 

Figure 1.8. Diagrammatic representation of an antibody molecule. An antibody molecule comprises two heavy chains (dark shading) and two light chains (unshaded). These chains are held together by disulphide (-S—S-) bonds. The site of papain cleavage (yielding Fab and Fc portions of the molecule) is shown. Each antibody molecule has two potential anti-gen-binding sites.

Figure 1.12. Schematic representation of an IgM molecule. Each IgM molecule comprises five IgG molecules joined by disulphide bonds and a J chain. Although the molecule has a predicted valency of 10 (i.e. a single IgM molecule can bind 10 molecules of antigen), this number is not reached in practice.

Figure 1.13. Schematic representation of an IgA molecule. Each IgA molecule comprises immunoglobulin molecules joined to each other via a J chain. The heavy chains possess three constant regions (Co1 Cce). The secretory chain (SC) is secreted by epithelial cells and binds to the IgA dimer via disulphide bonds (indicated by wriggly lines).

Figure 7.4 Basic structure of an IgG molecule. Two heavy chains (440 residues) and two light chains (214 residues) are joined by disulphide bonds and each shows a relatively constant amino acid sequence in one section (C-terminal end) and a variable sequence section (N-terminal end). The variable regions of both heavy and light chains are involved in the formation of the antigen-binding site.

Dithio-bis(inosinylimidodiphosphate) (66) forms mixed disulphides between the 6-thiol group of the purine and cysteine residues on myosin on binding four... 

Figure 3.31. Separation of proteins by SDS-PAGE. Protein samples are incubated with SDS (as well as reducing agents, which disrupt disulphide linkages). The electric field is applied across the gel after the protein samples to be analysed are loaded into the gel wells. The rate of protein migration towards the anode is dependent upon protein size. After electrophoresis is complete, individual protein bands may be visualized by staining with a protein-binding dye (a). If one well is loaded with a mixture of proteins, each of known molecular mass, a standard curve relating distance migrated to molecular mass can be constructed (b). This allows estimation of the molecular mass of the purified protein. Reproduced by permission of John Wiley Sons Inc. from Walsh (2002)...

The insulin receptor is a tetrameric integral membrane glycoprotein consisting of two 735 amino acid a-chains and two 620 amino acid )S-chains. These are held together by disulphide linkages (Figure 8.2). The a-chain resides entirely on the extracellular side of the plasma membrane and contains the cysteine-rich insulin-binding domain. 

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