Actin And Cell Motility (Topic3) Flashcards
G actin
Monomer, can be added to polymer when bound to ATP
F-actin
Polymer
-has polarity
Formin
Assemble unbranded filaments
- Fh1 domain
- fh2 domain
- activated by Rho (binds RBD sequence)
FH1 domain
Binds profilin and recruits g-actin ATP
FH2 domain
2 of these domains associate into donut shape and bind 2 actin subunits
Arp2/3
Nucleates branched filaments
-WCA protein WASp binds actin subunit
Cdc42
Activates WASp
Also involved in formation of filopodia
Thymosin
Decreases filament growth by binding g-actin ATP and preventing polymerization
Profilin
Increases filament growth, binds g-actin ADP and enhances switch to ATP
- can bind (+) end of actin filament
- increased expression during cell growth
Cofilin
Binds F-actin ADP bound subunits, causes filament to destabilize and break down
-causes tread milling in conjunction with profilin
CapZ
Binds (+) end and inhibits addition or loss
Tropomodulin
Bind (-) end and inhibits addition or loss
Gelsolin
May bind (+) end -with increased calcium, binds sides of actin filaments, inserts between subunits and creates shorter filaments
Cytochalasin D
Toxin, binds (+) end and blocks addition
Latrunculin
Toxin, binds and sequesters g-actin, inhibits addition to filament
Jasplakinolide
Toxin, enhances nucleation, binds actin diners, lowers critical concentration
Phalloidin
Toxin (angel of death mushroom)
Binds between subunits of f-actin and prevents depolymerization
ActA protein
Expressed on surface of Listeria, activates Arp2/3, forms branching complex that forms “comet tail” which propels listeria around the cell
alpha-actinin
Involved in formation of filopodia and stress fibres
- contractile bundles of muscle cells
- filaments arranges in opposite polarity
Fibrin, villin
- parallel bundles in filopodia and villi
- actin filaments close together, same polarity
Spectrin
Tetramer with 2 actin binding domains
Forms networks of filaments
Filamin
Flexible region with actin binding domain, creates cross links between filaments
Myosin
Motor protein, uses ATP to stimulate motion
Sarcomere
Structure with repeating myosin and actin filaments, slide against each other during contraction, stabilized by Tropomodulin, CapZ and nebulous
Nebulin
Extends along thin actin fibres in sarcomeres, determines length
Titin
Attaches thick filaments in Sarcomere to z-disk
Filopodia
Parallel bundles or actin in epithelial cells and fibroblasts
Lamellopodia
Flat network of actin in neural growth cones
Pseudopodia
3D network of actin in amoeba movement and phagocytosis
Rho
Helps form stress fibres
Activated Formin
Rac
Forms membrane Ruffles on leading edge, involved in formation of Lamellopodia through WAVp and arp2/3
Classes of intermediate filaments
Keratins (epithelial cells)
Desmin, vimentin (muscle, glia)
Neurofilaments
Lamins (nucleus)
