NMR constrained solution structures for laminin peptide 11. Analogs define structural requirements for inhibition of tumor cell invasion of basement membrane matrix.

Peptide 11, CDPGYIGSR-NH2, is a segment of laminin which blocks tumor cell invasion. A high affinity laminin receptor in tumor cells is thought to be blocked by the carboxyl-terminal YIGSR, and conformational energy calculations suggest that the glycine in YIGSR allows an important conformational bend. We replaced the YIGSR glycine residue in peptide 11 with either D-alanine or L-alanine to allow or disfavor the proposed glycine bend. We found the Gly7-->D-Ala7 analog to be equal to peptide 11 in inhibiting tumor cell invasion of basement membrane matrix. The Gly7-->L-Ala7 analog was much less capable of invasion inhibition. Two-dimensional 1H-1H NMR was used to study the solution conformations of the peptide 11 analogs. NOESY experiments revealed close NH-NH contacts in peptide 11 and the D-Ala7 analog, but not in the L-Ala7 analog. Molecular dynamics generated low energy structures with excellent NOE agreement for peptide 11 and its analogs. Both peptide 11 and the D-Ala7 analog, but not the less active L-Ala7 analog, were predicted to have similar bends around Gly7 or D-Ala7. These results suggest that a bend in the YIGSR region of peptide 11 may be important for the binding of laminin to its metastasis-associated receptor.