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Publication Abstract from PubMed

Coiled coils are the best-understood protein fold, as their backbone structure can uniquely be described by parametric equations. This level of understanding has allowed their manipulation in unprecedented detail. They do not seem a likely source of surprises, yet we describe here the unexpected formation of a new type of fiber by the simple insertion of two or six residues into the underlying heptad repeat of a parallel, trimeric coiled coil. These insertions strain the supercoil to the breaking point, causing the local formation of short beta-strands, which move the path of the chain by 120 degrees around the trimer axis. The result is an alpha/beta coiled coil, which retains only one backbone hydrogen bond per repeat unit from the parent coiled coil. Our results show that a substantially novel backbone structure is possible within the allowed regions of the Ramachandran space with only minor mutations to a known fold.

alpha/beta coiled coils.,Hartmann MD, Mendler CT, Bassler J, Karamichali I, Ridderbusch O, Lupas AN, Hernandez Alvarez B Elife. 2016 Jan 15;5. pii: e11861. doi: 10.7554/eLife.11861. PMID:26771248^[1]

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