A designed system for assessing how sequence affects alpha to beta conformational transitions in proteins.
The role of amino acid sequence in conformational switching observed in prions and proteins associated with amyloid diseases is not well understood. To study alpha to beta conformational transitions, we designed a series of peptides with structural duality; namely, peptides with sequence features of both an alpha-helical leucine zipper and a beta-hairpin. The parent peptide, Template-alpha, was designed to be a canonical leucine-zipper motif and was confirmed as such using circular dichroism spectroscopy and analytical ultracentrifugation. To introduce beta-structure character into the peptide, glutamine residues at sites away from the leucine-zipper dimer interface were replaced by threonine to give Template-alphaT. Unlike the parent peptide, Template-alphaT underwent a heat-inducible switch to beta-structure, which reversibly formed gels containing amyloid-like fibrils. In contrast to certain other natural proteins where destabilization of the native states facilitate transitions to amyloid, destabilization of the leucine-zipper form of Template-alphaT did not promote a transformation. Cross-linking the termini of the peptides compatible with the alternative beta-hairpin design, however, did promote the change. Furthermore, despite screening various conditions, only the internally cross-linked form of the parent, Template-alpha, peptide formed amyloid-like fibrils. These findings demonstrate that, in addition to general properties of the polypeptide backbone, specific residue placements that favor beta-structure promote amyloid formation.
Ciani
Barbara
B
Centre for Biomolecular Design and Drug Development, The School of Biological Sciences, University of Sussex, Falmer, Brighton BN1 9QG, United Kingdom.
Hutchinson
E Gail
EG
Sessions
Richard B
RB
Woolfson
Derek N
DN
D000465:Algorithms; D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry; D052160:Benzothiazoles; D002942:Circular Dichroism; D008854:Microscopy, Electron; D008956:Models, Chemical; D008962:Models, Theoretical; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D010452:Peptide Biosynthesis; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D013696:Temperature; D013844:Thiazoles / Q000737:chemistry; D013912:Threonine / Q000737:chemistry; D014461:Ultracentrifugation
D000682:Amyloid; D052160:Benzothiazoles; D010455:Peptides; D013844:Thiazoles; C009462:thioflavin T; D013912:Threonine; D010100:Oxygen