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BIO130 Section Two Guide (4)

3 Pages
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Department
Biology
Course Code
BIO130H1
Professor
Kenneth Yip

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Chapter 16 The Cytoskeleton
Molecular Motors
-Motor proteins bind to polarized cytoskeletal filaments and use the energy derived from ATP
hydrolysis to move (differ in cargo, direction of travel, type of filament they bind to)
oMany carry membrane-enclosed organelles (mitochondria, Golgi stacks, vesicles)
oGenerate motion by coupling ATP hydrolysis to a large-scale conformational change
in a protein
-The motor proteins associate with their filament tracks through ahead region or motor
domain that binds and hydrolyzes ATP
oThrough a mechano-chemical cycle of filament binding, conformation change,
filament release, conformational relaxation, and filament rebinding, the motor
protein and its associated cargo move one step at a time along the filament
The motor domain determines the identity of the track and the direction of
movement, the tail determines the identity of the cargo therefore, the
biological function of that motor protein
Actin-Based Motor Proteins are Members of the Myosin Superfamily
-Skeletal muscle myosin
generates the force for muscle
contraction myosin II is an
elongated protein that is formed
form two heavy chains and two copies of each of two light chains
oEach heavy chain has a globular head domain at its N-terminus that contains
the force-generating machinery, followed by a very long amino acid sequence that
forms an extended coiled-coil that mediates heavy chain dimerization
oThe two light chains bind close to the N-terminal head domain, while the long coiled-
coil tail bundles itself with the tails of other myosin molecules
Tail-tail interactions form large bipolarthick filaments that have hundreds
of myosin heads oriented in opposite directions at the two ends of the thick
filament
-Each myosin head binds and hydrolyzes ATP
uses the energy of ATP hydrolysis to walk towards the plus end of an actin filament
-The opposing orientation of the heads in the thick filament makes the filament efficient at
sliding pairs of oppositely oriented actin filaments past each other
-Myosins move towards the (+) end of an actin filament, but myosin VI moves to the
(-) end
There are Two Types of Microtubule Motor Proteins: Kinesins and Dyneins
-Kinesin moves along microtubules
oMost have the motor domain at the N-terminus of the heavy chain and walk toward
the (+) end of the microtubule (Some have their motor domain located at the C-
terminus walking in the opposite direction)
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Description
Chapter 16 The Cytoskeleton Molecular Motors - Motor proteins bind to polarized cytoskeletal filaments and use the energy derived from ATP hydrolysis to move (differ in cargo, direction of travel, type of filament they bind to) o Many carry membrane-enclosed organelles (mitochondria, Golgi stacks, vesicles) o Generate motion by coupling ATP hydrolysis to a large-scale conformational change in a protein - The motor proteins associate with their filament tracks through a head region or motor domain that binds and hydrolyzes ATP o Through a mechano-chemical cycle of filament binding, conformation change, filament release, conformational relaxation, and filament rebinding, the motor protein and its associated cargo move one step at a time along the filament The motor domain determines the identity of the track and the direction of movement, the tail determines the identity of the cargo therefore, the biological function of that motor protein Actin-Based Motor Proteins are Members of the Myosin Superfamily - Skeletal muscle myosin generates the force for muscle contraction myosin II is an elongated protein that is formed form two heavy chains and two copies of each of two light chains o Each heavy chain has a globu
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