Motor proteins

Question 1

What kind of proteins are they?

Answer 1

P loop ATPases

P-loop =GxxxxGKT

Switch 1 =NxxSSR

Switch 2 =DxxGxE

Question 2

What bind the neck domain of myosins?

Answer 2

Light chain at 2

Or calmodulins at 1 and 5

Question 3

Which experiments have alluded to the step size of myosin V?

Answer 3

Label one head green and the other red.

Leading head moves 36nm on graph.

Labelling just ONE head produces step size of 72nm showing HAND OVER HAND process ice mechanism.

Question 4

What is the consequence of the myosin ATPase cycle?

Answer 4

Dissociation of ADP from myosin is 100x slower in absence of Actin

Actin therefore stimulates ATPase activity of myosin

Relation to G proteins as actin is nt exchange factor for myosins.

Question 5

How is force produced by the ATPase cycle?

Answer 5

Small conformational change in head domain

Converter region at base of head amplifies it to rotate the lever like neck

Neck domain amplifies rotation –> AF moves.

Question 6

How does the myosin V cycle differ?

Answer 6

Steady state intermediate is AM.ADP