Motor Proteins Flashcards
What are the main types of molecular motor proteins?
Kinesin, dynein, and myosin
These motor proteins are essential for various cellular functions, including transport and movement.
How do motor proteins generate movement?
By using energy from ATP hydrolysis to change shape and move along tracks in eukaryotic cells
The process involves nucleotide binding and hydrolysis altering the shape of the motor proteins.
What type of filaments do myosins move along?
Actin filaments
Myosins are primarily involved in muscle contraction and cellular movement.
What type of structures do kinesin and dynein move along?
Microtubules
Kinesins typically move towards the plus ends, while dyneins move towards the minus ends.
Which motor protein is responsible for axonal transport?
Kinesin —> outward transport to axon terminal
Cytoplasmic dynein —> backward transport to the cell body
Vesicles take approximately 2 days to move down an axon that is 1 metre long
What is the role of cytoplasmic dynein?
It works with the partner complex dynactin to transport various cargoes
It binds to different adaptor proteins to move different types of cargo.
Fill in the blank: Kinesin moves towards the _______ ends of microtubules.
plus
This directional movement is crucial for cellular organization.
Fill in the blank: Dynein moves towards the _______ ends of microtubules.
minus
This allows for the transport of organelles and vesicles back towards the cell center.
What types of cargo do microtubule motors transport?
Membranous organelles, endosomes, lysosomes, mitochondria, nucleus, peroxisomes, Golgi apparatus
They are crucial for maintaining cellular organization and function.
What is the speed at which a vesicle of 50 nm diameter can move?
5 µm/sec
This speed can be scaled to larger distances to understand cellular transport rates.
What is the significance of the sliding filament theory?
It explains how myosin II walks along actin filaments to cause muscle contraction
This theory is fundamental to understanding muscle physiology.
What is the primary function of myosin II in animals?
Muscle contraction and movement
Myosin II is the best characterized member of the myosin superfamily = found in most animal cells types
What are stress fibers?
Contractile bundles formed by myosin II in non-muscle cells
They play a role in maintaining cell shape and motility.
What is the role of myosin I?
Short distance organelle movement and reshaping the plasma membrane by pulling on the underlying actin filaments
True or False: Myosins are used for long-distance membrane transport in animals.
False
Microtubule motors (kinesins and dyneins) perform long-distance transport in animal cells.
What is one example of a structure that dynein drives in cilia and flagella?
Axonemal dynein
This motor protein is essential for the beating motion of cilia and flagella.
What is the function of axonemal dynein?
Drives ciliary and flagellar beating
In isolated doublet Microtubules, dynein produces Microtubule sliding
In a normal flagellum, dynein causes Microtubule bending
Basic principles of motor proteins
- Use energy from ATP hydrolysis to move (nucleotide binding & hydrolysis alters shape of motor protein)
- Myosins move along actin filaments
- Kinesin and dynein family members move along Microtubules
How does Kinesin move along a Microtubule?
- ATP hydrolysis loosens attachment of head 1 to Microtubule
- ADP released and ATP binding changes conformation of head 2 which pulls head 1 forward
Main types of Kinesin
Eg5
Kinesin-1
2 types of dynein
Cytoplasmic dynein
Axonemal dynein —> ciliary and flagellar
Movement of ER
ER mainly moves outward using Kinesin but there is also some inward movement driven by cytoplasmic dynein
Movement of Golgi
Cytoplasmic dynein transports the Golgi apparatus toward the cell centre
How are viruses transported?
Transported from the plasma membrane to the nucleus by cytoplasmic dynein either within endosomes or as viral capsids
