title: Atomic structure of a tryptophan-zipper pentamer.
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.
authors.affiliation: Department of Biochemistry, Weill Medical College of Cornell University, New York, NY 10021, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
authors.forename: Wei
authors.initials: W
authors.lastname: Yong
authors.forename: Yiqun
authors.initials: Y
authors.lastname: Deng
authors.forename: Neville R
authors.initials: NR
authors.lastname: Kallenbach
authors.forename: Min
authors.initials: M
authors.lastname: Lu
mesh_terms: D020816:Amino Acid Motifs; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry*; D055672:Static Electricity; D014364:Tryptophan / Q000737:chemistry
chemical_list: D010455:Peptides; D014364:Tryptophan