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Publication Abstract from PubMed

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 beta-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 beta-sheet surface would result in large conformational changes and/or stabilization and thereby provide new means of controlling the properties of beta-sheets. Surprisingly, X-ray 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 beta-sheet conformation in protein design.

Aromatic cluster mutations produce focal modulations of beta-sheet structure.,Biancalana M, Makabe K, Yan S, Koide S Protein Sci. 2015 May;24(5):841-9. doi: 10.1002/pro.2657. Epub 2015 Mar 25. PMID:25645104^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.