To nucleate the assembly of branched actin filaments, Arp2/3 needs to be activated by a nucleation promoting factor (NPF)

TLS Online TPP Program

#Id: 8372

#Unit 2. Cellular Organization

Thick-filament regulation

Myosin-dependent mechanism regulate contraction in smooth muscle and non-muscle cells.

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#Id: 8373

#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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#Id: 8374

#Unit 2. Cellular Organization

When the Ca2+ levels drop:

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

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#Id: 8375

#Unit 2. Cellular Organization

Ca2+ dependence of vertebrate skeletal muscle contraction, depends on :

action potential

specialized accessory proteins Tropomyosin,

Troponin (T, I, and C)

TLS Online TPP Program

#Id: 8376

#Unit 2. Cellular Organization

Myosin 

Actin-based motors powered by ATP hydrolysis.

TLS Online TPP Program

#Id: 8377

#Unit 2. Cellular Organization

Myosins have 

Motor head domain

Lever-arm neck domain

Cargo-binding tail domain