Choose the best option for each part and explain why it is the correct answer: P

Question

Choose the best option for each part and explain why it is the correct answer:

Part 1: In myosin and other P-loop NTPase protein family members, Swtich-1 binds to ?_____

a. Myosin’s allosteric activator, actin

b. The actin-binding cleft

c. Myosin’s essential light chain

d. MgATP

The Relay-Helix

Part 2: Closing of the actin binding cleft correlates with_________.

a. Formation of the nanomolar affinity actomyosin complex

b. Formation of the micromolar affinity actomyosin complex

c. Formation of the myosin.ATP complex

d. Dissociation of the actomyosin complex

e. ATP hydrolysis

Part 3: The straight to bent structural transition of the myosin Relay helix is most tightly correlated with:

a. Opening of the switch-2 loop

b. Actin binding

c. Phosphorylation of the myosin regulatory light chain

d. The actin-activated myosin powerstroke

e. ATP hydrolysis

Part 4: The rate limiting biochemical kinetic step for ATP hydrolysis in the absence of actin is:

a. ATP binding

b. ATP hydrolysis

c. ADP dissociation

d. Phosphate dissociation

e. Actin binding

Explanation / Answer

Part 1: In myosin and other P-loop NTPase protein family members, Swtich-1 binds to ?_____

ANS: b. The actin-binding cleft

Part 2: Closing of the actin binding cleft correlates with_________.

ANS: e. ATP hydrolysis

Part 3: The straight to bent structural transition of the myosin Relay helix is most tightly correlated with:

ANS: b. Actin binding

ATP and actin control the structural dynamics of the myosin SH1/SH2 helix, the actin binding interface, the actin binding cleft, and the myosin relay helix.

Part 4: The rate limiting biochemical kinetic step for ATP hydrolysis in the absence of actin is:

ANS: c. ADP dissociation

ADP release is the rate limiting step of Microtubule activated ATPases.

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