Excitation-Contraction Coupling in Smooth Muscle

Which enzyme is responsible for the dephosphorylation of myosin light chains?

What happens to the affinity of the myosin head for ATP when myosin light chains are dephosphorylated?

What is the latch state?

Which of the following is a major difference between smooth muscle and skeletal/cardiac muscle in terms of cross-bridge cycle regulation?

Which enzyme phosphorylates myosin light chains in smooth muscle?

What activates myosin light chain kinase (MLCK) in smooth muscle?

Myosin Light Chain Regulation

Myosin light chain phosphatase (MLCP) is responsible for the dephosphorylation of myosin light chains, which plays a crucial role in muscle contraction regulation.
When myosin light chains are dephosphorylated, the affinity of the myosin head for ATP increases, leading to enhanced interaction with ATP during the muscle contraction cycle.

Latch State

The latch state refers to a unique phenomenon in smooth muscle where dephosphorylated myosin remains attached to actin for extended periods, maintaining tension with low energy consumption.

Muscle Types Comparison

A major difference between smooth muscle and skeletal/cardiac muscle in terms of cross-bridge cycle regulation is that smooth muscle relies more on the intracellular calcium levels to initiate contraction, whereas skeletal and cardiac muscles predominantly use excitation-contraction coupling.

Phosphorylation Mechanism

Myosin light chain kinase (MLCK) is the enzyme that phosphorylates myosin light chains in smooth muscle, facilitating muscle contraction.
MLCK is activated by the calcium-calmodulin complex in smooth muscle cells, which responds to increases in intracellular calcium concentration.

Test your knowledge on excitation-contraction coupling in smooth muscle. Learn about the interactions of actin and myosin, the role of calcium, and the ATP hydrolysis process. Discover the similarities and differences between smooth, skeletal, and cardiac muscle.