Coiled-coil assembly by peptides with non-heptad sequence motifs.
BACKGROUND
The seven-residue heptad repeat is the accepted hallmark of coiled coils. In extended filamentous proteins, however, contiguous patterns of heptads are often disrupted by 'skips' and 'stammers'. The structural consequences and roles of these digressions are not understood.


RESULTS
In a cytoskeleton protein from Giardia lamblia, heptads flank eleven-residue units (hendecads) to give a 7-11-7 motif that dominates the sequence. Synthetic peptides made to the consensus sequence of this motif fold in solution to fully helical, parallel dimers. Both the sequence pattern and these experimental data are consistent with the coiled-coil model. We note that breaks in other extended coiled coils can also be reconciled by hendecad insertions.


CONCLUSIONS
The heptad paradigm for the coiled coil must be expanded to include hendecads. As different combinations of heptads and hendecads will give different overall sequence motifs, we propose that these provide a mechanism to promote cognate protein pairings during the folding of extended coiled coils in the cell.
Hicks
M R
MR
Centre for Biomolecular Design and Drug Development, School of Biological Sciences, University of Sussex, Falmer, UK.
Holberton
D V
DV
Kowalczyk
C
C
Woolfson
D N
DN
D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D016384:Consensus Sequence; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000235:genetics; D019281:Dimerization; D016829:Giardia lamblia / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry* / Q000235:genetics; D017510:Protein Folding; D017433:Protein Structure, Secondary; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid
D003598:Cytoskeletal Proteins; D010455:Peptides; D015800:Protozoan Proteins