Synthetic peptides and proteins as models for pore-forming structure of channel proteins

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This chapter discusses a strategy to identify, in the primary structure of channel proteins, segments that determine the functional characteristics of the protein. Amphipathic α-helical segments are identified in the primary structure using secondary structure prediction algorithms. Segments are selected based on sequence similarity between members of a superfamily of channel proteins. Synthesis of the four-helix bundle protein is accomplished by a two-step procedure: the template molecule is synthesized using orthogonal lysine side-chain protection followed by the simultaneous assembly of peptide blocks. Oligomeric clusters of amphipathic α-helices, whether self-assembled in the lipid bilayer or covalently attached to a template molecule in a four-helix bundle configuration, form ionic channels in bilayers. The evidence that fundamental pore properties may be reproduced within a bundle of α-helices representing selected sequences from the primary structure of a channel protein lends credence to the notion that a cluster of amphipathic α-helices constitutes a general pore-forming motif for channel proteins. © 1992, Elsevier Inc. All rights reserved.

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Methods in Enzymology

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