Contractile Proteins Flashcards
What are actin bundles?
F-Actin that is cross-linked into closely packed parallel arrays by peptides/polypeptides
What are actin networks?
Actin that is loosely cross-linked in orthogonal arrays that form three-dimensional meshwork with gel-like properties
What are actin-bundling proteins?
Proteins that bind cross-linking F actin
What does fimbrin do?
Binds to actin filaments as a monomer, holding two parallel filaments close together
What are contractile bundles?
Actin i laments that are loosely bundled
What does alpha-actinin do?
Binds as a diner to separate filaments by a greater distance; allows for loose bundling
What does filamin do?
Large actin binding proteins; Binds actin as a dimer; binds actin filaments in networks
What does spectrin do?
Binds actin to create a mesh network to form a cytoskeleton (interacts with ankyrin and protein 4.1)
What is hereditary spherocytosis and its clinical manifestations?
A mutation in cortical cytoskeleton proteins in erythrocytes (spectrin, ankyrin, protein 4.1)
Decreased RBC (anemia)
Jaundice
Splenomegaly
What is pseudopodia?
An actin projection based on actin filaments cross-linked into a 3-D network, that are responsible for phagocytosis
What is lamelliopodia?
An actin projection that is a broad, sheet like extension at the leading edge of a cell, containing a network of actin filaments
What is filopodia?
A thin actin projection of the plasma membrane supported by actin bundles. The formation and retraction of these structures is based on the regular assembly and disassembly of actin filaments
What does myosin use to fuel movement?
ATP hydrolysis
What are the three major domains of myosin?
Head, neck and tail
Which myosin domain contains acting binding and ATP binding sites?
The head
Which myosin domain is the flexible region/binds myosin light chain peptides?
The neck
Which myosin domain binds membrane/organelles
The tail
Describe how myosin moves along F-actin?
In absence of ATP, myosin attaches to an actin filament
Binding of ATP causes a conformational change, releasing actin
Myosin remains in a cocked state until binding to actin
Binding of actin causes release of phosphate to drive power stroke (conformational change in the neck and moves actin filament)
Remains bound until ADP/ATP switch
How does the velocity of a longer neck compare to a shorter myosin neck?
A longer neck will have increased velocity
A low concentration of calcium correlates to what?
A folded state of myosin; relaxed state of muscle
A high concentration of calcium correlates to what?
Phosphorylation of myosin, causing it to unfold and become active
What causes cleavage furrow in cytokinesis?
Myosin movements along actin filaments of the contractile ring
Myosin V binds to what to become active?
Cargo
What is duchenne muscular dystrophy? And what causes it?
A progressive muscle wasting disease (x-linked recessive)
An out of frame mutation in the dystrophin gene which normally connects the cytoskeleton to the basal Lamina
