PMID: 15520380 , Related PDB id: 1T8Z

Authors:

Liu J, Yong W, Deng Y, Kallenbach NR, Lu M

Title:

Atomic structure of a tryptophan-zipper pentamer.

Journal:

Proc Natl Acad Sci U S A. 2004 Nov 16;101(46):16156-61. Epub 2004 Nov 1.

Abstract:

Coiled-coil motifs are ubiquitous mediators of specific protein-protein interactions through the formation of interlocking hydrophobic seams between alpha-helical chains. Residues that form these seams occur at the first (a) and fourth (d) positions of a characteristic 7-aa repeat and are primarily aliphatic. The potential of aromatic residues to promote helix association in a coiled coil was explored by engineering a "Trp-zipper" protein with Trp residues at all 14 a and d positions. The protein forms a discrete, stable, alpha-helical pentamer in water at physiological pH. Its 1.45-A crystal structure reveals a parallel, five-stranded coiled coil, a previously uncharacterized type of "knobs-into-holes" packing interaction between interfacial Trp side chains, and an unusual approximately 8-A-diameter axial channel lined with indole rings that is filled with polyethylene glycol 400 and water and sulfate ion molecules. The engineered Trp-zipper pentamer enlarges current views of coiled-coil assembly, molecular recognition, and protein engineering, and may serve as a soluble model for membrane ion channels.