Lecture 6 Flashcards
(31 cards)
List the 3 types of cytoskeleton components and their thickness
Microfilaments (actin) (7nm thick) Intermediate Filaments (8-10nm thick) Microtubules (25 nm in diameter)
Describe actin monomers
known as G-actin Has an ATP binding site Displays polarity (faces the same direction) when polymerized with other G-actin
Describe active filaments
long chains known as F-actin Organized into bundles and 3D networks
describe the structure of actin microfilaments
consist of a double helical chain of G-actin subunits
Describe the process of actin polymerization
ATP actin associates with the barbed (plus) end of actin and is then hydrolyzed to ADP after polymerization Monomers may bind to either end, but bind much faster to the barbed end
Define treadmilling
occurs when intermediate concentrations of G-actin favor a dynamic addition of monomers to the plus end, while monomers fall off of the pointed end
(Drugs that affect polymerization) Define Cytochlasins
bind to barbed ends of actin and block elongation This inhibits cellular movement, such as cell division
(Drugs that affect polymerization) Define Phalloidin
binds to actin filaments and prevents dissociation into monomers ○ Can be labeled with fluorescent dyes to visualize actin filaments
(actin binding molecules) define Spectrin
binds the cortical cytoskeleton to the plasma membrane Found in RBC’s
(actin binding molecules) define Dystrophin
Binds the cortical cytoskeleton to the plasma membrane
(actin binding molecules) define Villin and Fimbrin
Cross-links in microvilli
(actin binding molecules) define Calmodulin and Myosin I
cross-links plasma membrane in microvilli
(actin binding molecules) define Alpha-actinin
Cross-links stress fibers and connects actin to protein-plasma membrane
(actin binding molecules) define Filamin
Cross-links at wide angles to form screen-like gels
(actin binding molecules that control treadmilling) define Thymosin
Captures actin monomers and prevents them from being polymerized
(actin binding molecules that control treadmilling) define Profilin
regulates filament assemble by catalyzing the exchange of G-actin bound ADP for ATP This gets monomers ready to be polymerized
(actin binding molecules that control treadmilling) define Gelsolin
cuts F-actin and adds a cap at the cut to prevent loss/addition of G-actin
(actin binding molecules that control treadmilling) define Cofilin
triggers depolymerization of actin at the minus end
(actin binding molecules that control treadmilling) define Arp 2/3
causes branching from the sides of the F-actin filament
(actin binding molecules that control treadmilling) define Phalloidin
binds to actin filaments to prevent depolymerization
(actin binding molecules that control treadmilling) define Latrunculins
Binds to G-actin and induces F-actin depolymerization
Describe the structure of Intermediate filaments and differentiate it from microfilaments and microtubules.
Composed of 2 polypeptides, aligned tail to tail and head to head, and form a coiled dimer Dimers form tetramers in a staggered, antiparallel fashion (no distinct ends like actin) This makes them more stable and prevents treadmilling
Describe the heirarchial structure intermediate filaments
2 monomers form a dimer 2 dimers form a tetramer tetramers form protofilaments 8 protofilaments form filaments
describe the structure of a microtubule
Alpha and Beta units form Tubulin dimers (just the name of the bond) this forms microtubule protofilaments
