When a predicted coiled coil is really a single α-helix, in myosins and other proteins

Abstract

Naked single α-helices are unusual in proteins. Recently, we discovered that the predicted coiled-coil domain of some myosins was in fact a stable single α-helix (SAH). As a consequence these proteins do not dimerise through coiled-coil formation as previously assumed. As the SAH domain is well placed to lengthen the lever, it could enable these myosins to take larger steps than has been previously assumed. It is now becoming clear than a substantial number of diverse proteins contain this previously overlooked domain. SAHs are commonly misidentified as coiled-coil domains by prediction software and an initial scan for potential SAH sequences suggests that up to 4% of proteins in the human proteome predicted to have a coiled-coil domain actually have a SAH domain instead. This review summarises recent findings on SAH domains, their properties, their potential functions and some clues on how to recognise them.