Question

A small unique insert found near the end of the motor domain in myosin VI has been linked to the singular ability of this myosin to move toward the pointed end of actin filaments. If the unique insert is removed by genetic engineering, the resulting mutant myosin VI is a plus-end directed motor. This observation indicates that ...

A. the unique insert is necessary and sufficient for minus-end directionality.
B. the unique insert is necessary for motor activity.
C. the unique insert is necessary for plus-end directed directionality.
D. the unique insert is not sufficient for minus-end directionality.
E. None of the above.

Answer 1

The unique insert in myosin VI is necessary and sufficient for its movement towards the minus-end of actin filaments; removing this insert changes its direction, making it move towards the plus-end instead.

Step-by-step explanation:

The observation that removing the unique insert in myosin VI results in a mutant myosin VI that moves toward the plus end of actin filaments indicates that the unique insert is necessary for minus-end directionality. Since myosin VI normally moves towards the minus end of actin filaments and changes this behavior when the insert is removed, we can conclude that this insert is critical for determining the direction in which myosin VI moves. Therefore, the correct answer to the question is A. the unique insert is necessary and sufficient for minus-end directionality.