Regular Article
Direct Observation of Processive Movement by Individual Myosin V Molecules

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Abstract

Myosin V is an unconventional myosin thought to move processively along actin filaments. To have hard evidence for the high processivity, we sought to observe directly the movement by individual native chick brain myosin V (BMV) molecules with fluorescent calmodulin. Single BMV molecules did exhibit highly processive movement along actin filaments fixed to a coverslip. BMV continued to move up to the barbed end of its actin track, and did not readily detach from action. The barbed end, therefore, got brighter with time, because of a constant stream of BMV traffic. The maximum speed of the processive movement was 1 μm/s, and the maximum actin-activated ATPase rate was 2.4 s−1. These values apparently imply that BMV travels a great distance, 400 nm, per an ATPase cycle.

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