Chapter 14, Problem 1Q

If myosin V moved more like an “inchworm” (meaning it dragged its rear filament-binding domain forward, but not in a hand-over-hand fashion), how would a graph of spot movement over time differ from the one shown in Figure 14A-2b?

Summary Introduction

To determine: The way in which graph of spot movement over time differs from the graph shown in figure 14A-2b given in the textbook when myosin V moved like an inchworm.

Introduction: Myosin protein V is an important protein which is involved in the transports of various types of intracellular cargo along with actin proteins. These myosin proteins are involved in the transport of various membrane-bound organelles and show two alternating types of mechanisms for movement. One method is the hand-over-hand method and another method is the inch worm model.

Explanation of Solution

Hand-over-hand mechanism of myosin V movement states that the trailing head would move past the stationary forward head by an approximate distance of 74 nanometers to reach a new actin binding site. In contrast to this, the inch-worm model suggests that both heads would advance or move forward only by 37 nanometers during the step. Both trailing and leading heads do not undergo the process of position exchange during the inch worm model.

The best way to determine the difference between the hand-over-hand model and inch-worm models is to strictly follow the displacement of one of myosin V heads. Therefore, a graph of spot movement over time will differ in case of distance as 74 nanometers (position along actin filament) will be shown in the hand-over-hand model and 35 nanometers will be shown in inchworm model of spot movement.