Detection of post-translational sulfation of alpha-5 beta-1 integrin and its role in integrin-fibronectin binding

Fibronectins are glycoproteins of the extracellular matrix composed of two 220-kDa polypeptide chains named A and B bound by two disulfide bridges. Both chains when digested with proteolytic enzymes give rise to six different domains named I to VI that are involved in the ligand properties of this molecule. Fibronectins bind fibrin, collagen, glycosaminoglycan residues and several integrins. In this study, using metabolic radiolabeling of alpha(5)beta(1) integrin with sodium sulfate, an immunoprecipitation reaction, inhibition of sulfate incorporation an a fibronectin-binding assay, we were able to detect this integrin as a sulfated molecule and this sulfation appears to regulate the integrin-fibronectin binding.