Investigation of the Sequence to Structure Relationship of Beta-Helices from a Triple-Stranded Beta-Helix

The field of beta-helix design is lagging behind that of coiled-coil protein design. Challenges for designing beta-helical structures include inadequate sequence based structure prediction for beta-helices and the aggregation tendencies of these proteins, which are similar in structure to amyloids. Even more challenging is the design of the rare, triple-stranded beta-helix in which three strands of the same amino acid sequence must wrap around a common helical axis. Understanding the sequence and structural elements found in naturally occurring beta-helical structures and portions of beta-helices isolated from parent structures may provide insight on how to engineer such interesting, yet complex structures. Described here are my efforts to isolate triple-stranded beta-helices from a naturally occurring structure. Folding and stabilization of the constructs was improved with a trimer initiator attached at the C-terminus of the constructs. One beta-helical construct was systematically mutated to compare and understand critical features for the proper folding and stability of two different constructs isolated from the same parent beta-helical structure. We hope that the added knowledge of the sequence to structure relationship for the beta-helices studied in this work will allow for the development of both positive and negative design elements for the triple-stranded beta-helix.