Sidechain and backbone requirements for anti-invasive activity of laminin peptide 11

The structure of laminin peptide II (CDPGYIGSR-NH2) contains valuable infor mation for the design of mimetic compounds with anti-invasive and anti-meta static properties. An alanine scan replacement experiment identified Tyr(5) , Ile(6) and Arg(9) residues as contributing significantly to anti-invasive activity. Circular dichroism spectra and NMR alpha H chemical shift values both supported the existence of populations of nonrandom coil solution str uctures for the analogs tested. A D-Ala(4) for Gly(4) substituted analog co mpletely lost activity, while an L-Ala(4) for Gly(4) substituted analog ret ained half the activity of the parent peptide. These results complement our previous findings with D/L alanine substitutions at the Gly(7) position, a nd together they suggest an 'S'-shaped backbone as likely for the active pe ptide conformation. NMR-constrained molecular modeling supported a direct i nvolvement of the Tyr(5) and Ile6 sidechains in conferring bioactivity, and indicated that the Tyr(5) sidechain was buried in the Ala(2) for Asp(2) su bstitution. Based on the fact that the peptide 11 sequence derives from the disulfide bonded c-loop of an LE-repeat, we synthesized the cyclic <(CDPGY IGSRC)under bar>-NH2 peptide. This analog exhibited good anti-invasive and anti-metastatic activity. NMR modeling experiments suggested that the trans -proline cyclic peptide, would favor an 'S'-shaped backbone conformation. F ull retro-inverso analogs of peptide 11 were shown to have anti-invasive ac tivity inferior to that of peptide Il. This weak bioactivity was probed usi ng NMR-constrained molecular dynamics, and revealed potential conformations which limited the ability of the required sidechains to mimic the position s of those in the native peptide conformations. (C) 1998 Elsevier Science B .V. All rights reserved.