The aggregated form of an AAMP derived peptide behaves as a heparin sensitive cell binding agent

A peptide termed P189, derived from the sequence of a newly discovered protein, AAMP (angio-associated migratory cell protein), contains a motif that is predicted to a bind heparin. It occurs near the amino terminal end of AAMP. Previous studies have shown that in its solubilized form P189 (RRLRRMESESES) binds heparin and melanoma cells. The peptide is bipolar in that it contains positive charges at its amino end and negative charges at its carboxyl end. It forms strongly aggregated particles that require exposure to 50% DMSO and 100 degrees C for solubilization to occur. Now heparin and cell binding (heparin sensitive) are also demonstrated for the peptide in its particular form. Cell binding/clustering to the peptide particles is strong and resists exposure to various reagents (sugars and inhibitors of glycolysis and protein synthesis) except heparin. Tumor cell migration is partially inhibited by the presence of the peptide. On electron photomicrographs the peptide is seen in close apposition to cell membranes. Heparin sensitivity of the cell binding indicates that cell surface glycosaminoglycans are involved. The aggregated peptide binds heparin in a saturable manner with a dissociation constant, K(d), of 306 pmol. Cell binding/clustering studies using peptide variants of P189, which have substitutions in either the charged and/or nonpolar residues, show that the specific sequence of P189 optimizes heparin-sensitive cell aggregation. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 365-372, 1997.