Author(s): Koivunen E, Gay DA, Ruoslahti E
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Abstract The alpha 5 beta 1 integrin binds fibronectin through the integrin recognition sequence Arg-Gly-Asp (RGD). We have used a 6-amino acid peptide library expressed on filamentous phage to identify peptide ligands for alpha 5 beta 1. We found that this integrin selectively binds RGD-containing peptides from the library. Of the 32 different sequences obtained, 28 had the RGD motif, 3 contained sequences related to RGD, and only 1 had a clearly different sequence. One of the RGD-containing phage encoded a potentially cyclic insert CRGDCL. The cyclic peptide GAC*RGDC*LGA (where * denotes cysteines forming a disulfide bond) was 10-fold more efficient than any of the linear RGD-containing hexapeptides in inhibiting the binding of RGD-expressing phage to alpha 5 beta 1 or the attachment of alpha 5 beta 1-expressing cells to fibronectin. This peptide also inhibited cell attachment mediated by the alpha v beta 1, alpha v beta 3, and alpha v beta 5 integrins with about 10-fold higher efficiency than linear GRGDSP. One peptide containing an RGD-related sequence, NGRAHA, was also found to inhibit phage attachment and cell adhesion, especially adhesion mediated by the alpha v beta 5 integrin. These results indicate that novel and high affinity ligands for integrins can be isolated from a random peptide library.
This article was published in J Biol Chem
and referenced in Journal of Molecular Biomarkers & Diagnosis