Determinants of processivity in the single-headed class IX myosins

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Myosins are a large family of diverse mechanoenzymes that bind to Factin and hydrolyse ATP to produce mechanical force. Different myosin molecules differ substantially in their motor properties such as speed, force, step size, direction, processivity, interplay with the track and regulation of these properties. These differences in motor properties allow myosins to adopt many different cellular functions. The class IX myosins move processively along actin filaments taking multiple steps before they dissociate from the actin filament. This is exceptional because they are single-headed and spend a considerable amount of time in the ATP-bound state that is a state with weak affinity for F-actin in other myosins. We hope to elucidate the mechanism of single-headed processive movement and to identify the necessary adaptations for it. These studies will lead to a better understanding of the general mechanisms of actin-based molecular motors, single motor processivity and the cellular functions of the multi-domain class IX myosins that are simultaneously negative regulators of the small monomeric G-protein Rho.