Post-assembly α-helix to β-sheet structural transformation within SAF-p1/p2a peptide nanofibersElectronic supplementary information (ESI) available. See DOI: 10.1039/c8sm01754a

• Main Authors: Roberts, Evan K, Wong, Kong M, Lee, Elizabeth J, Le, Melina M, Patel, Dipam M, Paravastu, Anant K
• Format: Journal Article
• Language: English
• Published: 14.11.2018
• ISSN: 1744-683X; 1744-6848
• DOI: 10.1039/c8sm01754a

We report an unanticipated helix-to-sheet structural transformation within an assembly of SAF-p1 and SAF-p2a designer peptides. Solid-state NMR spectroscopic data support the assembled structure that was targeted by rational peptide design: an α-helical coiled-coil co-assembly of both peptides. Subsequent to assembly, however, the system converts to a β-sheet structure that continues to exhibit nearest-neighbor interactions between the two peptide components. The structural transition occurs at pH 7.4 and exhibits strongly temperature-dependent kinetics between room temperature (weeks) and 40 °C (minutes). We further observed evidence of reversibility on the timescale of months at 4 °C. The structural conversion from the anticipated structure to an unexpected structure highlights an important aspect to the challenge of designing peptide assemblies. Furthermore, the conformational switching mechanism mediated by a prerequisite α-helical nanostructure represents a previously unknown route for β-sheet designer peptide assembly. The SAF-p1/p2a binary peptide system co-assembles in water into α-helical coiled coils, but can convert post-assembly into a β-sheet structure.