Aromatic cluster mutations produce focal modulations of ?-sheet structure.

ABSTRACT: 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 ?-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 ?-sheet of Borrelia outer surface protein A (OspA). This unusual ?-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 ?-sheet surface would result in large conformational changes and/or stabilization and thereby provide new means of controlling the properties of ?-sheets. Surprisingly, X-ray crystal structures revealed that the introduction of aromatic clusters produced only subtle conformational changes in the OspA ?-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 ?-sheet conformation in protein design.

SUBMITTER: Biancalana M 

PROVIDER: S-EPMC4420532 | biostudies-literature | 2015 May

REPOSITORIES: biostudies-literature