Term
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Definition
•Actin is most abundant protein in cell
–Muscle cell contains 10% actin by weight
–Non muscle cell contains 1-5%
•Actin monomer ~375 aa residues
–Highly conserved in all eukaryotes
•Actin is most common member of actin-related proteins (ARPs)
–Arp2/3 50% identical to actin, Required for actin nucleation
–Arp1- required for cytoplasmic dynein function (microtubule motor)
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Term
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Definition
•Muscle
•At cleavage furrow during cytokinesis
•Cell movement and edge growth
•Vesicle trafficking
•Microvilli in intestinal brush border
•Stereo cilia in ear
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Term
Rate Limiting Step for Polymerization? |
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Definition
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Term
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Definition
–Monomers are added to one end and removed from the other end. Polymer retains a constant length with a net flux of subunits through the filament.
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Term
Regulation of polymerization: |
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Definition
•Regulation of nucleation- protein factors that regulate nucleation
–Arp complex and Formin proteins nucleate actin filaments.
•Regulation of elongation-factors that alter the rate of elongation.
–End specific capping proteins regulate dynamics.
•Regulation by severing filaments- factors that cut the middle of filaments.
–Filament severing enhances dynamics (gelsolin)
•Regulation of G-actin
–Profilin facilitates exchange of ADP for ATP on G actin monomers, Proflin-actin binds to + end of filament, allowing for rapid polymerization
–thymosin - binds to G actin and prevents polymerization.
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Term
Actin-based movement requires growth from barbed(+) ends. This can be achieved by: |
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Definition
•de novo nucleation of filaments
•uncapping of barbed ends by loss of capping protein
•Severing actin filaments
•all three mechanisms likely contribute to cell motility but de novo nucleation appears to be the most important
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Term
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Definition
-is key actin nucleator
-nucleates more efficiently when bound to the side of an actin filament
- normally controlled by members of the WASP protein family
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Term
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Definition
•Member of a large family of related proteins
–Act as a scaffolds for actin nucleation
–Required for cell motility, endocytosis, exocytosis
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Term
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Definition
-family of at least 15 distinct proteins
-responsible for forming parallel bundles and unbranced filaments
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Term
Conventional skeletal myosin (myosin II)
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Definition
–ATP-dependent movement of myosin on actin filament
-The muscle myosin II forms biopolar thick filaments
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Term
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Definition
- regulation of by phosphorylation
-required for cell movement
Roles
•Cell movement
•Organelle transport
–Melanosome transport
•mRNA transport
•Chitin localization
•Endocytosis/Exocytosis
•Cell differentiation
•Signal transduction
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Term
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Definition
–single head, low processivity but low ATP hydrolysis rate
–membrane binding site
–protrusion of actin-rich structures at the cell surface
–function to provide cortical tension
–but also found in the nucleus
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Term
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Definition
–double head low processivity
- work in large groups
–fast
–muscle movement, cytokinesis cell motility
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Term
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Definition
–double head, high processivity
–tails are specialized for binding cargo
–localization of vesicles, organelles and mRNAs
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