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Structure of myosin molecules

The head-head interaction that switches off activity in thick filaments is also found in isolated myosin molecules.  This suggests a common mechanism for turning off cell motility and muscle contraction. Using negative staining EM and single particle reconstruction we have determined the structural basis of this switching. The off-state involves folding of the myosin tail into three segments that wrap around the heads. Interaction of the tail with the heads interferes with ATP hydrolysis and actin binding. It also blocks a phosphorylation site required to switch on activity.  Added to the inhibition created by interaction between the heads, this completely shuts down activity in the molecule, thus explaining the extraordinary inhibition of the off-state measured biochemically (Yang et al., J Gen Physiol., 2019). We are currently focusing on the molecular details of the inhibitory interaction using high-resolution cryo-EM.

Craig Lab - UMMS - 10S-myosin