Synthesis, NMR and function of an O-phosphorylated peptide, comprising the RGD-adhesion sequence of osteopontin

The bone phosphoprotein osteopontin owes its cell adhesion property to the RGD-sequence. In order to determine whether a phosphate substituent on the serine following the RGD-sequence interferes with cell binding, we have synthesized GRGDSL along with the corresponding peptide phosphorylated on serine. The latter peptide showed significantly lower cell binding as measured by inhibition of adhesion of R1 cells to surfaces coated with BSP. GRGDSL and phosphorylated GRGDSL show NMR spectra which resemble each other more than that of GRGDSP derived from the fibronectin sequence.