Nuclear export mechanism are of two types:

Ran-dependent nuclear export

Ran-independent nuclear export

TLS Online TPP Program

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#Unit 2. Cellular Organization

Smooth muscle contraction is regulated by the cycling of myosin II between on and off states.

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#Unit 2. Cellular Organization

In vertebrate smooth muscle, phosphorylation of the myosin regulatory light chain activates contraction in Ca2+ dependent manner.

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#Unit 2. Cellular Organization

When the Ca2+ level rises, Ca2+ binds CaM.

TLS Online TPP Program

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#Unit 2. Cellular Organization

The CaM*-Ca2+ complex binds and activates MLC kinase, phosphorylates the myosin LC. 

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#Unit 2. Cellular Organization

Phosphorylation of MLC 

unfolds the myosin II, active and can assemble into bipolar filaments for contraction

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#Unit 2. Cellular Organization

When the Ca2+ levels drop:

Myosin LC is dephosphorylated by MLC phosphatase, causing muscle relaxation.