Question

Question 1 20 pts Cytochalasin is a drug that caps actin filament plus ends, thus preventing actin polymerization. Phalloidin is a drug that binds to and stabilizes actin filaments, preventing actin depolymerization. Even though these drugs have opposite effects on actin polymerization, the addition of either of these drugs instantaneously freezes the cell movements that depends on actin filaments. Explain why drugs that have opposite effects on actin filaments can have a similar effect on cell movements.

Answer 1

Actin is an structural protein present in eukaryotes . Actin filament network are required for cell locomotion. Actin filament are linear polymers of globular actin subunits Cytochalasin is a cell permeable toxin bind to the end of actin filament inhibiting subunits association and dissociation and thus prevent them from polymerisation into filament whereas phalloidin stabilizes actin filament by decreasing dissociation of actin subunits hence prevent actin filament depolymerisation .

Cytochalasin help in growth of filament near membrane that pushes cell forward whereas phalloidin causes depolymerisation of actin fialment away from the plasma membrane ,as a result both drugs activity freezes the cell movement .