High-Resolution Crystal Structure of an Artificial (βα)8-Barrel Protein Designed from Identical Half-Barrels

摘要

Ample evidence suggests that the ubiquitousn(u0001R)8-barrel enzyme fold has evolved by the duplicationnand fusion of an ancestral (u0001R)4-half-barrel. To reconstructnthis process in the laboratory with a model protein, wenearlier fused two copies of the C-terminal half-barrelnHisF-C of imidazole glycerol phosphate synthase (HisF)nand stepwise stabilized the resulting HisF-CC construct.nWe now further increased its stability and solubility bynintroducing two additional amino acid exchanges, whichnallowed us to crystallize the resulting artificial (u0001R)8-barrelnprotein HisF-C***C. The analysis of its X-ray structurenat 2.1 Å resolution reveals a striking similarity to wildtypenHisF, helps us to understand its improved stability,nand provides further insights into the evolution of (u0001R)8-nbarrel proteins.