Figure 3.

The N-terminal extension of skeletal ELC(A1) or cardiac ELC modifies myosin step-size in muscle. Muscle myosin can perform an 8 nm step shown in panel a or two other shorter steps of 5 or 3 nm depicted in panel b. The 5 nm step forgoes the ELC/actin interaction and is predominant in porcine cardiac and rabbit skeletal muscle. The 3 nm step is the rare separation of a full 8 nm step into two shorter steps, possibly owing to slow dissociation of ADP. We show here that adult zebrafish skeletal myosin uniquely has equal propensity for 5 and 8 nm steps. Panel a also indicates lever-arm rotation angle Φ from the angle formed from ∠cde and lever-arm length ℓ used in equation (2.4).