Aromatic cluster mutations produce focal modulations of beta-sheet structure

作者：Biancalana Matthew; Makabe Koki; Yan Shude; Koide Shohei^*

来源：Protein Science, 2015, 24(5): 841-+.

DOI：10.1002/pro.2657

• protein design
• conformational stability
• beta-sheet formation
• secondary structure

Site-directed mutagenesis is a powerful tool for altering the structure and function of proteins in a focused manner. Here, we examined how a model beta-sheet protein could be tuned by mutation of numerous surface-exposed residues to aromatic amino acids. We designed these aromatic side chain "clusters" at highly solvent-exposed positions in the flat, single-layer beta-sheet of Borrelia outer surface protein A (OspA). This unusual b-sheet scaffold allows us to interrogate the effects of these mutations in the context of well-defined structure but in the absence of the strong scaffolding effects of globular protein architecture. We anticipated that the introduction of a cluster of aromatic amino acid residues on the b-sheet surface would result in large conformational changes and/or stabilization and thereby provide new means of controlling the properties of beta-sheets. Surprisingly, Xray crystal structures revealed that the introduction of aromatic clusters produced only subtle conformational changes in the OspA beta-sheet. Additionally, despite burying a large degree of hydrophobic surface area, the aromatic cluster mutants were slightly less stable than the wild-type scaffold. These results thereby demonstrate that the introduction of aromatic cluster mutations can serve as a means for subtly modulating b-sheet conformation in protein design.

• 出版日期2015-5