Structures of single-layer ?-sheet proteins evolved from ?-hairpin repeats.

ABSTRACT: Free-standing single-layer ?-sheets are extremely rare in naturally occurring proteins, even though ?-sheet motifs are ubiquitous. Here we report the crystal structures of three homologous, single-layer, anti-parallel ?-sheet proteins, comprised of three or four twisted ?-hairpin repeats. The structures reveal that, in addition to the hydrogen bond network characteristic of ?-sheets, additional hydrophobic interactions mediated by small clusters of residues adjacent to the turns likely play a significant role in the structural stability and compensate for the lack of a compact hydrophobic core. These structures enabled identification of a family of secreted proteins that are broadly distributed in bacteria from the human gut microbiome and are putatively involved in the metabolism of complex carbohydrates. A conserved surface patch, rich in solvent-exposed tyrosine residues, was identified on the concave surface of the ?-sheet. These new modular single-layer ?-sheet proteins may serve as a new model system for studying folding and design of ?-rich proteins.

SUBMITTER: Xu Q 

PROVIDER: S-EPMC6699103 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature