What is the primary mechanism by which the actin cytoskeleton generates cell motility?
- Polymerization/Depolymerization driven: Filament assembly or disassembly can create the motility w help from Profilin and Arp2/3. The process of ATP hydrolysis occurs and treadmilling to give the motility ??
- Myosin motors: also act to generate motility through a process of binding, the POWER STROKE and unbinding, generating the contractile force for movement.
****What effect does ATP hydrolysis have on actin and actin filaments?
- Irreversible step for actin subunits, result is ADP-actin with Pi. seen in cytoskeleton and mechanisms of movement
- Treadmilling results: Giving the effect of a monomer moving on a treatmill. the ADP bound actin at pointed end dissociate, at a faster rate than the ATP-bound actin can associate. ATP-bound must associate faster to catch up
What are the different types of microfilament arrays seen in different cell types and what are their functions? Please see the textbook for a more complete discussion of these arrays than what I covered in class.
- Near actin periphery:
- In Brush Border Epithelial Tissue: aid in SURFACE EXPANSION
- In Plant epidermis: aid in CYTOPLAMIC FLOWING
- In RBCs: act as STRUCTURAL MATRIX for membrane STABILITY
- Microfilament functions: Absorption, secretion and Cell motility role
- In Amoeboid: actin role in CELL CRAWLING
- Intracellular motility
- Contractile rings in Rat Kidney and Fission Yeast
- Muscle fibers in vertebrae
- Stress fibers in Amoeboid cells
What is the relationship between actin and the Arp proteins?
- Arp: Actin related proteins that are 60% identical to actin But do NOT form FILAMENTS. Have same contacts with ATP but different surfaces
- Related in that Arp2/3: involved in NUCLEATING Branched ACTIN FILAMENTS
- Arps are involved in vesicle formation and microtubule based transport