Flashcards in The Cytoskeleton: Part 2 Deck (36):
The dynein motor protein complex is a ______ _____ that moves towards the _____ end
What is dynein?
a large protein complex; associated with other protein complexes that together transport cargo along microtubules
Dynein uses ATP to...
move along the microtubule
What is the difference between dynein movement and kinesin movement?
dynein movement: towards the cell body (minus end)
kinesin movement: towards the axon terminus (plus end)
What three processes are microfilaments/actin filaments involved in?
1. cell motility
2. contractile activity
What are microfilaments made of? (five things, including shape and structure)
1. actin monomers
4. helical filaments
5. two protofilaments
Myosin is a ____ _____
Microfilaments are composed of a single type of _____ protein.
Are actin filaments polar? Why or why not?
yes; due to the regular orientation of actin monomers in each protofilament
Which end is the tail? Head? (plus or minus)
Free monomers are bound to _____ which is bound in the _____ of the protein
What is actin?
ATPase; hydrolyzes ATP
ATP hydrolysis occurs more rapidly after...
actin monomers have been incorporated into the filament
Growth of the filament is faster at the _____ end; actin filaments have an _____ _____
What is actin filament treadmilling?
-although an actin filament looks stable, there is continual exchange of monomers at the ends
-occurs at a very specific concentration range
What occurs at each end at the treadmilling concentration?
plus end: net addition
minus end: net loss
The ____ end has a higher affinity for actin monomers than the ____ end
Myosin has tails of...
the two heavy chains organized in a coiled-coil (of alpha-helices)
Heads of the heavy chain are associated with four _____ _____
light chains (2 at each head)
ATP is hydrolyzed by the myosin head or tail?
Myosin is a family of
What kind of domains are conserved within the myosin family?
What is myosin II?
The _____ of myosin II along actin filaments causes muscles to _____
Myosin is a _____ filament. Actin is a _____ filament
Describe the myosin/muscle cell contractile apparatus.
1. myosin attached to an actin filament
2. ATP binding releases myosin from actin
3. ATP hydrolysis occurs along with a conformational change that displaces the myosin head
4. myosin binding to actin releases the Pi triggering the force-generating shape change
5. At the end of the cycle myosin is in the initial conformation but has moved to a new position in the actin filament
What is the main actin motor protein?
myosin II, plus end directed
What are the two microtubule motor proteins?
dynein, minus end directed
kinesin, plus end directed
What are two common mechanisms of motor proteins?
1. they all couple ATP hydrolysis with conformational changes to generate force
2. all move in a specific direction along filaments that have polarity (plus/minus end)
Intermediate filaments are involved in what kind of support?
Intermediate filaments are not found in _____ and _____
plants and animals
A coiled-coil dimer forms a staggered antiparallel tetramer and has no...
no filament polarity and no known motor proteins
What is a tetramer?
soluble form of a coiled coil dimer (staggered)
Intermediate filaments are prominent in cells subjected to mechanical stress including... (3 types of cells)
1. epithelial cells - keratin
2. neurons - neurofilament proteins
3. muscle cells - desmin
Filaments in epithelial cells are anchored at sites of ____-____ contact by ______. It also involves _____ strength.