Microtubule Motor Protiens And Cilia/flagella Flashcards
In regards to transport why are microtubules important
The transport membranous vesicles from one membrane compartment to another (ex, ER to golgi)
Transport non membrane bound cargo such as rna ribosomes or cytoskeletal elements
What are motor protiens
They use atp hydrolysis to make mechanical forces that move it and the cargo it’s carrying along the cytoskeleton
Move unidirectionally in a stepwise way
What are some examples of the cargo that motor protiens carry
Membranous vesicles
Non membrane bound material (rna, ribosomes)
Organelles (lysosome,mitochondria)
Chromosomes
Other cytoskeletal filaments
What are the three types of motor protiens
Microtubule motor protiens: walk on microtubules
Kinesins
Dyenins
Actin motor protiens: walk on actin
Myosins
What is the kinesin 1 superfamily
Just called kinesin and it’s a tetramer made of two heavy chains and 2 light chains intertwined
It has a globular head which bind to microtubules and move through ATP hydrolysis
Has a tail that bind to an adapter that binds to the cargo it’s carrying
The sequences of the kinesin globular head are
The sequences of the kinesin tails are
Conserved, same across other kinesin family’s
Diverse, diff evertime
How does the kinesin motor protien move along the microtubule
It moves toward the positive end of the tubule with the head only interacting with the beta tubulins
The leading head hydrolyzes one atp to make ADP and Pi which give energy for the power stroke that swings the trailing head (behind) forward
So per one ATP hydrolysis is one step
This moves the motor protiens 8nm ahead (length of one tubulin dimer)
Kinesin movement is highly processive, what does this mean
It can move large distances without falling off
It’s speed is proportional to the ATP concentration (max speed of 1micrometer per second)
One microtubules head is always attached to the tubules this is called the
Hand over hand movement
What is the structure of dynein
It’s head is 10x larger than kinesins, it walks faster too (larger steps)
It has two heavy chains and many intermediate/light chains
It has a tail that binds to that cargo though the adaptor protien dynactin
Has a globular head that generates force and atp hydrolysis to move
Which way does dynein move
What is its role
Toward the minus (alpha tubulin) end of the microtubule
It positions the spindle and moves the chromosome during mitosis
Positions organelles and vesicles
What is the retrograde and anterograde movement of the motor protein across the microtubules
Retrograde is moving from the + end to the - end of the microtubule (Dyneins)
Anterograde is moving from - to + (kinesins)
Kinesins and dyenins move ____
Similar things in opposite direction on the same microtubule
What is the postive run , pause , and negative run of motor protiens
Kinesins and dynein are both attached to the cargo, during the postive run the Kinesins are in control and moving to the + end
If it wants to change directions, the pause occurs and then the negative run where dynein take ms controls and moves towards the negative end
What are cilia and flagella
Hairlike organelles that protect outward from many eukaryotic cells
The have the same structure but different functions
Different from bacterial flagella
What is cilia specifically
Motile cilia move fluid (ex. In the respiratory tract they sweep mucus away from lungs)
They are very abundant on the cells surface
Have coordinated beating (power stroke and recovery stroke)
What is flagella
They help the entire cell move
What is the structure of cillia/flagella
The cillia/flagella are both extend out and continue from the cells plasma membrane
The axoneme makes up the cillia/flagella protrusions
The main microtubule organizing centre (centrosome) is at the basal body (which is the - end (the bottom)
The plus end is the distal end (the part sticking out)
What is the axonemes structure
2 microtubules in the centre
9 microtubule A and B doublets around them (9 + 2 array)
The doublets are connected to each other through nexin
What actually makes the cillia and flagella move
The axonemal dynein (dynein in cillia/flagalla) has its tail anchored to the A tubule in the microtubule doublets
It has its stalks (head) bound to the B tubule on a doublet next to it
The A tubule is like the cargo, so the dynein moves toward the negative end and move the a tubule with it during the power stroke atp hydrolysis
How do the cillia and flagella doublet microtubules stop from just completely sliding off each other
Nexin (the thing that binds the doublets to each other) stops them
Basically a push and pull mechanism
