High-Resolution Structure of a Self-Assembly-Competent Form of a Hydrophobic Peptide Captured in a Soluble [beta]-Sheet Scaffold

• Published in: Journal of molecular biology Vol. 378; no. (2) ; 04, 2008
• Main Authors: Makabe, Koki, Biancalana, Matthew, Yan, Shude, Tereshko, Valentina, Gawlak, Grzegorz, Miller-Auer, Hélène, Meredith, Stephen C., Koide, Shohei
• Format: Journal Article
• Language: English
• Published: United States 08.02.2010
• Subjects: AQUEOUS SOLUTIONS; CRYSTAL STRUCTURE; MATERIALS SCIENCE; PEPTIDES; POLYPEPTIDES; PROTEINS; STABILITY
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2008.02.051

{beta}-Rich self-assembly is a major structural class of polypeptides, but still little is known about its atomic structures and biophysical properties. Major impediments for structural and biophysical studies of peptide self-assemblies include their insolubility and heterogeneous composition. We have developed a model system, termed peptide self-assembly mimic (PSAM), based on the single-layer {beta}-sheet of Borrelia outer surface protein A. PSAM allows for the capture of a defined number of self-assembly-like peptide repeats within a water-soluble protein, making structural and energetic studies possible. In this work, we extend our PSAM approach to a highly hydrophobic peptide sequence. We show that a penta-Ile peptide (Ile{sub 5}), which is insoluble and forms {beta}-rich self-assemblies in aqueous solution, can be captured within the PSAM scaffold in a form capable of self-assembly. The 1.1-{angstrom} crystal structure revealed that the Ile{sub 5} stretch forms a highly regular {beta}-strand within this flat {beta}-sheet. Self-assembly models built with multiple copies of the crystal structure of the Ile5 peptide segment showed no steric conflict, indicating that this conformation represents an assembly-competent form. The PSAM retained high conformational stability, suggesting that the flat {beta}-strand of the Ile{sub 5} stretch primed for self-assembly is a low-energy conformation of the Ile{sub 5} stretch and rationalizing its high propensity for self-assembly. The ability of the PSAM to 'solubilize' an otherwise insoluble peptide stretch suggests the potential of the PSAM approach to the characterization of self-assembling peptides.