Structure-activity relationship of human bone sialoprotein peptides.

In the current study, the relationship between the structure of the RGD-containing human bone sialoprotein (hBSP) peptide 278-293 and its attachment activity toward osteoblast-like (MC3T3) cells was investigated. This goal was accomplished by examining the comparative cell-attachment activities of several truncated forms of peptide 278-293. Computer modeling of the various peptides was also performed to assess the role of secondary structure in peptide bioactivity. Elimination of tyrosine-278 at the N-terminus resulted in a more dramatic loss of cell-attachment activity compared with the removal of either tyrosine-293 or the arg-ala-tyr (291-293) tripeptide. Although replacement of the RGD (arg-gly-asp) peptide moiety with peptide KAE (lys-ala-glu) resulted in a dramatic loss of cell-attachment activity, a peptide containing RGE (arg-gly-glu) in place of RGD retained 70-85% of the parental peptide's attachment activity. These results suggest that the N-terminal RGD-flanking region of hBSP peptide 278-293, in particular the tyrosine-278 residue, represents a second cell-attachment site that stabilizes the RGD-integrin receptor complex. Computer modeling also suggested that a β-turn encompassing RGD or RGE in some of the hBSP peptides may facilitate its binding to integrins by increasing the exposure of the tripeptide. This knowledge may be useful in the future design of biomimetic peptides which are more effective in promoting the attachment of osteogenic cells to implant surfaces in vivo.