What are the 2 main parts of a molecular motor?
- A head which binds to the filaments and move along
- A tail that drags along cargo (organelles, vesicles)
The walking heads are at the ___ terminus while the cargo holding tails are at the ___ terminus
N terminus, C terminus
What are molecular motors mainly used for in the body?
Muscle contraction, ciliary beating and cell division
What are actin-based motor proteins called?
They are called myosins (I or II)
What are the different types of motor proteins?
Myosins (actin), kinesins, and dyneins
What are the types of myosins?
Myosin I, Myosin II, and Myosin II filament (perhaps there is a myosin VI?)
Describe Myosin I
Has one head (N terminus), a tail which binds to actin or the membrane
Describe Myosin II
Has two head (N terminus) and the two tails are coiled around each other until it is one coiled tail. (dimer)
Describe Myosin II filament
A bunch of myosin I but the tails are all connected in the middle and the several hundred heads point in opposite directions
While most Myosins will walk towards the plus end, Myosin ____ will walk to the minus end
Myosin VI is the odd one out apparently
Describe the process of myosin motor movements
Moves along the actin. It is bound to ATP but when it docks on the actine filament the Pi is released turning into ADP. Being bound to ADP causes the other catalytic core to disconnect while the other one is bound to actin. ADP is released and ATP binds again causing the head to detach and revert to its original form
Attached->released->cocked->force generating->attached
What is the difference between myosins and kinesins/dyneins?
Myosins are a motor on intermediate filaments. Kinesins and Dyneins are motors on microtubules.
Kinesins are ___ ended motor. As in they walk towards that direction
Plus ended
Dyneins are ____ ended motors. They walk towards that direction
Minus ended
T/F Myosins and Kinesins have a common evolutionary origin
True. Their heads have a similar structure
In kinesins, the leading head is always bound to A_P and the lagging head is always bound to A_P
ADP , ATP
Describe the mechanochemical cycle of kinesin
Leading head is bound to ADP, the lagging head is bound to ATP and both are bound to the microtubule. The rear head is hydrolyzed (loses a Pi) and loosens its grip on the microtubule. ATP replaces the ADP in the front head which makes the neck linker catapult the rear head forward (This is one step)
Does Kinesin or Myosin spend more time in its detached state?
Kinesin majority of the time being detached
T/F Myosin II spends very little time bound to the filament
True. This allows for rapid muscle movement and relaxation
What are the only things we need to know about Dynein?
- It is a large protein
- It walks to the minus end
The End
What are some examples of Microtubule motor based transport in the body?
- Cilia/flagella movement
- chromosome segregation
- Fish skin pigmentation video from lecture (dynein makes the pigments congregate in splotches)
- More (but I'm too tired to rewrite from last deck)
How is myosin II filament production regulated?
By MLK no jk its by MLCK (/Myosin Light Change Kinase). Is active if phosphorylated and assembles themselves. If not then its not. The end