Structural and inhibitory properties of a plant proteinase inhibitor containing the RGD motif

Abstract

Purified from Bauhinia rufa seeds, BrTI is a Kunitz proteinase inhibitor that contains the RGD sequence. BrTI inhibits trypsin ( K iapp 2.9 nM) and human plasma kallikrein ( K iapp 14.0 nM) but not other related enzymes. The synthetic peptide YLEPVARGDGGLA-NH 2 (70 μM) inhibited the adhesion to fibronectin of B16F10 (high-metastatic B16 murine mouse melanoma cell line) and of Tm5 (murine melanoma cell lines derived from a non-tumorigenic lineage of pigmented murine melanocytes, melan-a). YLEPVARGEGGLA-NH 2 in which Asp 9 was changed into Glu does not affect the cell attachment. Moreover, this peptide was functional only when the sequence present in the native protein was preserved, since YLIPVARGDGGLA-NH 2 in which Glu 3 was changed into Ile does not interfere with B16F10 and was less effective on Tm5 cell line adhesion. Neither YLEPVARGDGGLA-NH 2, YLIPVARGDGGLA-NH 2 or YLEPVARGEGGLA-NH 2 inhibit the interaction of RAEC (endothelial cell line from rabbit aorta) with fibronectin.