α-helical coiled coils: simple models for self-associating peptide and protein systemss

Abstract

Protein-protein recognition and protein oligomerization functions are among the important roles played by the α-helical coiled coil motif. As part of a study into the equilibrium and kinetic aspects of the folding of model coiled coils, an investigation into the stoichiometry and magnitude of the associative constants by sedimentation equilibrium in the ultracentrifuge has been initiated. A series of interrelated model peptides, with sequence lengths of about 30 residues, has been designed, synthesized and characterized. Each of the peptides has been subjected to conventional sedimentation equilibrium analysis under a variety of conditions. The stoichiometry of self-association has been established and it has been shown that, contrary to the expected result, most of the peptides formed trimeric systems of varying stability. The effect of substituting large hydrophobic constituents of the interacting interfaces of the systems with other similar residues has been shown to have minimal effect on trimer formation. However, substitution of such residues in the central sequence positions with either alanine or asparagine leads to a marked decrease in the stability of the trimeric state.