Contractile Proteins Flashcards
Actin bundles
Cross-linked into closely packed parallel arrays.
Can be closely associated or loosely associated.
Actin networks
Loosely cross-linked in orthagonal arrays that form 3D meshwork with gel-like properties.
Closely spaced actin filaments
Supports projections of PM (microvilli).
Fimbrin binds actin filaments and holds them close.
Loosely bundled actin filaments
For contraction.
Allows myosin to interact during contraction.
Networks of actin
Found beneath PM.
Aids in movement, stability.
Ex: spectrin.
Pseudopodia
Cross-linked actin in a network.
Facilitates phagocytosis.
Lamellipodia
Broad, sheet-like extensions at the edge of cell.
Filopodia
Thin projections of PM. Formation/retraction based on actin assembly.
Myosin domains
Head: actin binding and ATP binding sites. ATPase activity.
Neck: Flexible region. Binds myosin light chain peptides.
Tail: Intertwine to bring myosin heads closer. Binds organelles/membrane.
Myosin and actin movement overview
ATP binds causes conformation change ad releases actin.
Myosin binds actin and releases Pi and drive spower stroke.
Remains bound until ADP/ATP switch.
Velocity is dependent on:
Length of myosin neck.
Smooth and non-muscle cell contractions
Have different types of actin-myosin structures that are much less stable.
Some are transient interactions.
Cytokinesis
Bundles of f-actin and myosin II form contractile ring.
Myosin moves along actin filaments creating cleavge furrow.
Duchenne Muscular Dystrophy
Mutation in dystrphin gene. Dystrophin-glycoprotein complex provides structurand ECM which stabilizes the sarcolemma and prevents contraction induced injury.
