Antiparallel four-stranded coiled coil specified by a 3-3-1 hydrophobic heptad repeat.
Coiled-coil sequences in proteins commonly share a seven-amino acid repeat with nonpolar side chains at the first (a) and fourth (d) positions. We investigate here the role of a 3-3-1 hydrophobic repeat containing nonpolar amino acids at the a, d, and g positions in determining the structures of coiled coils using mutants of the GCN4 leucine zipper dimerization domain. When three charged residues at the g positions in the parental sequence are replaced by nonpolar alanine or valine side chains, stable four-helix structures result. The X-ray crystal structures of the tetramers reveal antiparallel, four-stranded coiled coils in which the a, d, and g side chains interlock in a combination of knobs-into-knobs and knobs-into-holes packing. Interfacial interactions in a coiled coil can therefore be prescribed by hydrophobic-polar patterns beyond the canonical 3-4 heptad repeat. The results suggest that the conserved, charged residues at the g positions in the GCN4 leucine zipper can impart a negative design element to disfavor thermodynamically more stable, antiparallel tetramers.
Department of Biochemistry, Weill Medical College of Cornell University, New York, New York 10021, USA.
Yiqun
Y
Deng
Jie
J
Liu
Qi
Q
Zheng
David
D
Eliezer
Neville R
NR
Kallenbach
Min
M
Lu
D050976:Basic-Leucine Zipper Transcription Factors; D018360:Crystallography, X-Ray; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D057927:Hydrophobic and Hydrophilic Interactions; D016350:Leucine Zippers; D008958:Models, Molecular; D009154:Mutation; D020449:Repetitive Sequences, Amino Acid; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics
D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; C501391:GCN4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors