Coiled coils consist of two to five amphipathic alpha-helices that twist around one another to form a supercoil which can be left-handed or right-handed. Left handed ones show a seven-residue periodicity and the right handed one a 11 residue periodicity the stability of which is achieved by a knobs-into-holes packing of apolar side chains into a hydrophobic core.

By modulation of their polar interactions, many different properties like extreme thermo stability can be achieved. Coiled coils are involved in signal transduction or molecular recognition. They provide mechanical stability to cells and are involved in movement process. Charged residues are frequently found at coiled coil interfaces.

The building blocks of IF architecture is an elongated coiled coil region (which inturn contains monomeric 1A and dimeric 1B, 2A and 2B sub segments connected by short linkers) flanked by non helical end domains. The dimeric 2B contains a discontinuity in the heptad repeat pattern called a stutter that creates an undecad repeat which is important for its structural integrity. The highly conserved region within the C-terminus of 2B has an inter-helical and intra-helical salt bridge.

There are several software products to predict the coiled coil region of proteins based on the above structural peculiarities.

Peter Burkhard et al. Coiled Coil: a highly versatile protein folding motif. Trends in Cell Biology 2001:11(2); 82-8

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