Expression of soluble, recombinant alpha v beta 3 integrin fragments in Escherichia coli

No prokaryotic expression of integrin alpha v beta 3 has been reported so far. We report here the expression of C-terminally truncated alpha v beta 3 receptors in E. coli considering the known features required for dimerization and ligand binding. The expressed protein was insoluble despite of the addition of `solubilizers' to the culture medium. Osmotic stress conditions combined with added exogenous solutes resulted in a small part of soluble receptor. The alpha v beta 3 variants were purified from inclusion bodies or from soluble cytoplasmic maltose binding protein fusions. Heterodimerization of the subunits was proved by immunoprecipitation assays. Receptor-ligand binding was found to depend on the concentration. A competition assay with RGD peptides referred to unspecific receptor-ligand interaction. The latter fact was consistent with the finding that soluble receptors did not bind on RGD peptide-coupled sepharose (GRGDSPK sepharose).