RGD sequence

In another study, the original repetitive Cio, (AGAGAGPEG)io, center was reconstructed into nine repeats of AGAGAGPEG with three distributed repeats of the RGD sequence. The new triblock protein, composed of acidic and basic terminal domains in addition to the reconstructed central block, has been shown to support adhesion, spreading, and polarization of human fibroblast cells [82]. Triblock polypeptides that facilitate antibody binding have also been reported [83]. 

Figure 48-3. Schematic representation of fibronectin. Seven functional domains of fibronectin are represented two different types of domain for heparin, cell-binding, and fibrin are shown. The domains are composed of various combinations of three structural motifs (I, II, and III), not depicted in the figure. Also not shown is the fact that fibronectin is a dimer joined by disulfide bridges near the carboxyl terminals of the monomers. The approximate location of the RGD sequence of fibronectin, which interacts with a variety of fibronectin integrin receptors on cell surfaces, is indicated by the arrow. (Redrawn after Yamada KM Adhesive recognition sequences.

Cationic glycosyl-bisporphyrins 66 and 6757 and a neutral porphyrin dimer 68 containing a pentapeptide moiety with RGD sequence as a spacer have also been prepared (Fig. 7).58... 

The binding of integrins to certain ligands is mediated by a short amino acid sequence. Thus, the binding site for fibronectin is confined to a sequence of four amino acid residues, Arg-Gly-Asp-Ser (RGDS) (R7). Synthetic peptides containing the RGDS sequence prevented adhesion of cells to fibronectin (B4, R7) and also inhibited metastasis formation in animal models (B4, R7). 

Probably the smallest sequence known to be responsible for receptor recognition is the RGD-tripeptide, initially discovered in fibronectin [143]. However, the specificity of the interaction with different integrins, the counter receptors of RGD sequences on the cell surface, is established by the flanking sequences of the RGD motif and the conformation of the tripeptide. In other words, the presentation of the RGD sequence is important for specific recognition by individual integrins. 

The presence of the tripeptide RGD sequence, and its crucial role in the cell-attachment process, were found subsequently in vitronectin [32, 133], fibrinogen [134], von Willebrand factor [134], type I collagen [135], and many other proteins present in body fluids and extracellular matrices [136],... 

Brandley and Schnaar [140] immobilized a synthetic nonapeptide, Tyr- Ala-Val Thr-Gly Arg-Gly-Asp-Ser, on a polyacrylamide gel, which had been prepared by a ternary copolymerization of acrylamide, bisacrylamide and the acrylic ester of. V-hydroxysuccinimide. They reported that Balb/c 3T3 mouse fibroblast cells (in Hepes-buffered Dulbecco s modified Eagle medium) adhered readily to the peptide-derivatized surfaces, even in the absence of serum, although long-term cell growth required the presence of serum. It was noticed that reference nonapeptide. Tyr-Arg-Leu-Glu-Asp-Pro-Ala-Met-Trp, which has no RGD sequence, failed to promote cell-attachment. 

The RGD sequence was thus constrained into a variety of sheet or /3-turn structures, which were unequivocally determined for each peptide. The biological activity of 18 cyclic peptides was then compared with that of a linear standard, GRGDS, in inhibition assays of tumour cell adhesion. An increase in activity of up to 100-fold was observed for just two cyclic pentapeptides, all others showing a decrease in activity. This identified the required conformation of the RGD backbone. 

Archaeobacteria 7, 815 Area detector for X-rays 134 Arg-Gly-Asp (RGD) sequence 408 Arginase 888... 

Several potent inhibitors of fibrinogen binding to gpIIb/IIIa are now known, and some have proven to be effective antithrombotic agents. These inhibitors tend either to be small cyclic peptide mimetics, in which the conformation of an RGD sequence is constrained by macrocyclization, or they are non-peptidic molecules containing functional group mimetics of the Arg and Asp side chains, held in the correct geometry for interaction with the receptor. Examples of both classes are shown in... 

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