Cytoplasmic Dynein Mechanism

Question 1

Which direction does dynein move?

Answer 1

Towards minus end

Question 2

What does dynein move along?

Answer 2

Microtubules

Question 3

What is the function of dynein?

Answer 3

• Involved in transporting cellular cargo
• Providing forces and displacements important in mitosis

Question 4

What is the general strutcture of dynein?

Answer 4

• Heavy chain heterdimer with multiple light chains

Question 5

What binds cargo in dynein?

Answer 5

~160 kDa N-terminal domain which binds multiple light chains

Question 6

In dynein what does dimerisation require?

Answer 6

Multiple diverse accessory subunits

Question 7

How big is the motor domain of dynein?

Answer 7

~380 kDa

Question 8

What is the structure of the motor in each heavy chain of dynein?

Answer 8

Contains 6AAA+ ATPase units which fold into a ring structure

Question 9

What does the linker structure of dynein do during powerstroke?

Answer 9

Moves across the AAA+ ring

Question 10

What extends from the AAA+ ring of dynein?

Answer 10

A coiled coil and microtubule binding site

Question 11

What is the structure of an AAA+ module?

Answer 11

• Contains a large and small subunit domain
• Small subdomains pack against large domains of next module

Question 12

how many ATPase sites are there on the AAA+ motor of dynein?

Answer 12

2

Question 13

Which AAA modules of dynein possess walker A domain motifs?

Answer 13

AAA 1-4

Question 14

What is the principal ATPase site in AAA+ motors of dynein?

Answer 14

AAA1

Question 15

What is the function of AAA3 module of dynein motor?

Answer 15

Regulates communication between linker and AAA1

Question 16

How does dynein communication changes driven by ATP hydrolysis into the microtubule binding domain?

Answer 16

• Via the stalk, 2 alpha helices of coiled coil slide past each other
• changes in the ring are communicated as pulling and pushing of coiled coil alpha helices changes conform of MTBD

Question 17

Is dynein as processive as kinesin?

Answer 17

No

Question 18

What does the axial path of dynein show?

Answer 18

It is variable and indicates that dynein can step between protofilaments

Question 19

What mechanism does dynein use to move?

Answer 19

Both inchworm and hand-over-hand

Question 20

What is the average step size for dynein?

Answer 20

16nm

Question 21

How far does the cargo move on average in dynein per step?

Answer 21

8nm

Question 22

Why is it useful for dynein to be able to step between protofilaments?

Answer 22

Kinesin moves the opposite direction so allows for the ability to switch paths and avoid kinesin

Question 23

How can adaptor proteins alter dynein motor activity?

Answer 23

by binding to cargo or altering the number of dyneins present

Question 24

Give 2 examples of dynein adaptor proteins

Answer 24

• Dynactin
• BICD2

Question 25

What happened to motor activity of dynein when dynactin and BICD2 were added?

Answer 25

It became more processive

Question 26

Why might adding dynactin and BICD2 to dynein make it more processive?

Answer 26

* May be due to altering of motor activity * Scaffolds for binding multiple dyneins

Question 27

What experiment can be done to determine if single or multiple dyneins are being used?

Answer 27

* Make dyneins labelled with either pink or green chemicals * When both labels are present it appears white * Use single molecules fluoscence microscopy * Stack images to track where things are bound

Question 28

Were the majority of processive events for dynein monomers or multimers?

Answer 28

Monomers