Cell-surface proteins

Antiparallel beta (P) structures comprise the second large group of protein domain structures. Functionally, this group is the most diverse it includes enzymes, transport proteins, antibodies, cell surface proteins, and virus coat proteins. The cores of these domains are built up by p strands that can vary in number from four or five to over ten. The P strands are arranged in a predominantly antiparallel fashion and usually in such a way that they form two P sheets that are joined together and packed against each other. 

Many other cell-surface proteins involved in immunological recognition utilize immunoglobulin-like domains as structural elements. Immunoglobulin domains have been classified into five types, namely V (like antibody variable... 

C, which is found in complement proteins FI, F2, and F3, first found in fibronectin I, the immunoglobulin superfamily domain N, found in some growth factor receptors E, a module homologous to the calcium-binding E-F hand domain and LB, a lectin module found in some cell surface proteins. (Adapted from Baron, M., Norman, D., and Campbell, I., 1991, Protein modnles. Trends in Biochemical Sciences 16 13—1 7.)... 

Forty-four amino acid module characterized by three internal disulfide bridges and an octahedrical cage for a calcium ion. Complement-type repeats are found in many cell surface proteins and form the ligand-binding domain of receptors of the LDL receptor gene family. 

Figure 2. (1) Neutrophils circulating passively in blood capillary. (2) Chemoattractants may be detected by the circulating neutrophils, by the endothelial cells lining the lumen, or both in order that the neutrophils become adhesive. This adhesion is mediated by selectins, a group of cell surface proteins. Neutrophils roll on the surface of the endothelial cells and then actively locomote seeking out spaces between the endothelial cells. (3) The adhesive neutrophils begin to squeeze between endothelial cells. (4) Cells move through the extracellular matrix towards the site of infection. Here adhesion is low and may not be necessary for locomotion. (5) At the site of infection, neutrophils become trapped by increased adhesion where they phagocytose bacteria and liberate the contents of their granules. After Lackie (1982,1986).

UB Sleytr, P Messner, D Pum, M Sara, eds. Crystalline Bacterial Cell Surface Proteins. Austin, TX Landes/Academic, 1996. 

Jacobsson, K., Jonsson, H., Lindmark, H., Guss, B., Lindberg, M., and Frykberg, L. (1997). Shot-gun phage display mapping of two streptococcal cell-surface proteins. Microbiol. Res. 152, 121-128. 

Young, R., Arnette, J., Roess, D. and Barisas, B. (1994). Quantitation of fluorescence energy transfer between cell surface proteins via fluorescence donor photobleaching kinetics. Biophys. J. 67, 881-8. 

Chen, I., Choi, Y. A. and Ting, A. Y. (2007). Phage display evolution of a peptide substrate for yeast biotin ligase and application to two-color quantum dot labeling of cell surface proteins. J. Am. Chem. Soc. 129, 6619-25. 

Maurel, D., Comps-Agrar, L., Brock, C., Rives, M. L., Bourrier, E., Ayoub, M. A., Bazin, H., Tinel, N., Durroux, T. Prezeau, L. et al. (2008). Cell-surface protein-protein interaction analysis with time-resolved FRET and snap-tag technologies Application to GPCR oligomerization. Nat. Methods J, 561-7. 

The isolated cells may be lysed using standard mechanical or detergent methods and the biotinylated cell-surface proteins analyzed or isolated using (strept)avidin reagents. 

The Cryptosporidium parasite attaches to the host s intestinal epithelium, becomes intracellular but remains extracytoplasmic. In vitro studies suggest that attachment is mediated by a Cryptosporidium parvum sporozoite ligand and an intestinal epithelial cell surface protein interaction [83, 84],... 

Most T-helper cells express a membrane protein termed CD4 on their surface. Most T-cytotoxic and T-suppressor cells produce a different cell surface protein, termed CD8. Monoclonal antibodies specifically recognizing CD4 or CD8 proteins can thus be used to differentiate between some T cell types. 

Binding of IFN-y to its surface receptor on polymorphonuclear neutrophils induces increased expression of the gene coding for a neutrophil cell surface protein capable of binding the Fc portion (i.e. the constant region see also Box 13.2) of IgG. This greatly increases the phagocytotic and cytotoxic activities of these cells. 

The biologically active form of M-CSF is a homodimer (two identical subunits). These homodimers can exist as integral cell surface proteins, or may be released from their producer cell by proteolytic cleavage, thus yielding the soluble cytokine. The M-CSF receptor is a single-chain, heavily glycosylated, polypeptide of molecular mass 150 kDa. 

Neurexins a protein kinase. A component of active zones that interact with RIM, syntaxin and other proteins. Cell surface proteins with more than 1,000 isoforms generated by alternative splicing from three genes. Neurexins include one of the receptors for aratrotoxin and may function in cell-cell recognition between neurons. 

The receptor for NGF is TrkA, a 140 kDa cell surface protein that specifically binds NGF, but not other neurotrophins [5, 6, 9]. TrkA is expressed on the neuronal cell body and on neuronal processes. In its action as a target-derived trophic factor, NGF is secreted within the target organ and it then binds to TrkA receptors present on the growing neuronal process or synapse. The NGF-TrkA complex is then internalized and subsequently translocated to the cell body by retrograde axonal transport. In those cells that respond to NGF through autocrine or paracrine mechanisms, the growth factor can bind to any of the widely distributed TrkA molecules on the neuronal membrane. 

The interest in using saccharide-substituted polymers to bind and cluster cell surface proteins arises from studies of L-selectin, a protein involved in inflammation. L-selectin binds glycoproteins that display complex carbohydrates, and... 

We and others have demonsttated that an endothelial, cell surface protein-disulfide isomerase-mediated mechanism, does exist for the rapid influx of RSNO bound-NO (Zai et al. 1999 Ramachandran et al., 2001). Whether the csPDI route plays a role in the transfer of NO-equivalents from RBCs remains to be answered. 

Ramachandran, N., Root, P., Jiang, X. M., Hogg, P. J., Mutus, B., Mechanism of transfer of NO from extracellular S-nitrosothiols into the cytosol by cell-surface protein disulfide isomerase, Proc. Natl. Acad. Sci. USA 98 (2001), p.9539-9544... 

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