Effects of mutations in the three lac operators

All three operators are essential for effective repression.

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When the Ca2+ levels drop:

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

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Sarcomere

Within each skeletal muscle cell are many myofibrils consisting of a repeating array of a specialized structure

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#Unit 2. Cellular Organization

Each sarcomere contains two major types of filaments: 

Thick filaments (myosin II)

Thin filaments (actin and associated proteins)

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Z disk 

Thin actin filaments are assembled with their (+) ends embedded in a densely staining structure

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In the presence of ATP and Ca+2 , the myosin heads extending from the thick

filaments walk toward the (+) ends of the thin filaments.

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The structure of the sarcomere is maintained by a number of accessory proteins: 

1. CapZ 

2.Tropomodulin

3.Titin 

4.Nebulin