There are RNA polymerase crystal structures that provide considerable insight into how the enzyme retains contact with its substrate while breaking and remaking bonds in the process of the nucleotide addition cycle and undergoing translocation by a Brownian ratchet mechanism.

TLS Online TPP Program

#Id: 1396

#Unit 4. Cell Communication and Cell Signaling

All small GTPases of the Ras superfamily, Cdc42, Rac, and Rho act as molecular switches, inactive in the GDP-bound state and active in the GTP-bound state.

TLS Online TPP Program

#Id: 1397

#Unit 4. Cell Communication and Cell Signaling

Actin-based motors powered by ATP hydrolysis.

TLS Online TPP Program

#Id: 1398

#Unit 4. Cell Communication and Cell Signaling

Myosins have 

  Motor head domain

  Lever-arm neck domain

  Cargo-binding tail domain

TLS Online TPP Program

#Id: 1399

#Unit 4. Cell Communication and Cell Signaling

The first myosin discovered

Myosin II, was isolated from skeletal muscle.

TLS Online TPP Program

#Id: 1400

#Unit 4. Cell Communication and Cell Signaling

Three classes of myosins:

Myosin I

Myosin II

Myosin V

TLS Online TPP Program

#Id: 1401

#Unit 4. Cell Communication and Cell Signaling

Myosin I

single head domain

Function- Membrane association, endocytosis