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Publication Abstract from PubMed

In coiled-coil (CC) protein structures alpha-helices wrap around one another to form rope-like assemblies. Most natural and designed CCs have two-four helices and cyclic (Cn) or dihedral (Dn) symmetry. Increasingly, CCs with five or more helices are being reported. A subset of these higher-order CCs is of interest as they have accessible central channels that can be functionalised; they are alpha-helical barrels. These extended cavities are surprising given the drive to maximise buried hydrophobic surfaces during protein folding and assembly in water. Here, we show that alpha-helical barrels can be maintained by the strategic placement of beta-branched aliphatic residues lining the lumen. Otherwise, the structures collapse or adjust to give more-complex multi-helix assemblies without Cn or Dn symmetry. Nonetheless, the structural hallmark of CCs-namely, knobs-into-holes packing of side chains between helices-is maintained leading to classes of CCs hitherto unobserved in nature or accessed by design.

Maintaining and breaking symmetry in homomeric coiled-coil assemblies.,Rhys GG, Wood CW, Lang EJM, Mulholland AJ, Brady RL, Thomson AR, Woolfson DN Nat Commun. 2018 Oct 8;9(1):4132. doi: 10.1038/s41467-018-06391-y. PMID:30297707^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.