The specificity factor (W) estimates the preference of rubisco for CO2 versus O2

where Vc and Vo  are the maximum velocities for carboxylation and oxygenation, respectively, and Kc and Ko are the Michaelis–Menten constants for CO2 and O2, respectively

TLS Online TPP Program

#Id: 1380

#Unit 4. Cell Communication and Cell Signaling

The critical concentration (Cc) is the concentration of free G-actin at which the filaments are formed.

TLS Online TPP Program

#Id: 1381

#Unit 4. Cell Communication and Cell Signaling

At steady state, ATP–G-actin subunits add preferentially to the (+) end, while ADP–G-actin subunits disassemble from the (−) end, giving rise to treadmilling of subunits.

TLS Online TPP Program

#Id: 1382

#Unit 4. Cell Communication and Cell Signaling

Profilin enhances the exchange of ADP for ATP on G-actin. Cofilin enhances the rate of loss of ADP-actin from the filament (−) end. Thymosin-β4, binds to ATP–G-actin in such a way that it inhibits addition of the actin subunit to either end of the filament.

TLS Online TPP Program

#Id: 1383

#Unit 4. Cell Communication and Cell Signaling

Formin protein nucleate the assembly of unbranched filaments, (FH1 and FH2 domains-Actin nucleation by the formin FH2 domain).

Formins are activated by membrane-bound Rho-GTP, a Ras-related small GTPase.

The Arp2/3 Complex Nucleates Branched Filament Assembly.

TLS Online TPP Program

#Id: 1384

#Unit 4. Cell Communication and Cell Signaling

Toxins affect the dynamics of actin polymerization; some, 

Latrunculin

Phalloidin

Cytochalasin D

Jasplakinolide

TLS Online TPP Program

#Id: 1385

#Unit 4. Cell Communication and Cell Signaling

There are three classes of myosins, are present in many eukaryotes: 

Myosin I- single head domain

Myosin II- two heads and assembles into bipolar filaments

Myosin V- two heads but does not assemble into filaments