CONFORMATIONAL BEHAVIOR OF A SYNTHETIC PEPTIDE OF THE C-TERMINUS OF VILLIN THAT INTERACTS WITH ACTIN - AN NMR, CD AND SIMULATED ANNEALING STUDY

The solution structure of a synthetic 22-amino acid peptide (P1) corre sponding to the extreme C-terminal end and one of the F-actin binding sites of villin has been determined by H-1 NMR and CD spectroscopy. Th e structure of this peptide was compared to that of a peptide in which lysine to glutamic acid substitutions were introduced at positions 17 and 19 (P11), abolishing F-actin binding. Both peptides are largely u nstructured in aqueous solution. Changes observed in the NMR and CD sp ectra of both peptides are consistent with a-helix formation in triflu oroethanol/water mixtures. A set of 189 interproton distances derived from nuclear Overhauser enhancement (NOE) measurements, 17 Phi-angle c onstraints obtained from (3)J(NH alpha), coupling constants, as well a s about 10 N ... O distance restraints deduced from amide proton excha nge kinetics with deuterium, were used for the structure determination . The three-dimensional structure of P1 and P11 is characterized by tw o helical regions, one extending from residues 2 to 5 and a second cov ering residues 7 to 17. The central fragment, ranging from Leu-7 to Le u-15, is more stable. The C-terminal residues are less structured, par ticularly within peptide P11. The significance of these structural res ults is discussed in relation to the biological activity of villin. (C ) Munksgaard 1995.