Motor proteins

Question 1

Give different functions of the kinesins.

Answer 1

1 for vesicles and organelle transport

2 for intraflagellar transport

10 for chromosome positioning.

Question 2

What are the three models for bidirectional organelle transport?

Answer 2

Competition (activities and numbers of motors)

Biochemical coupling (motor interaction on cargo coordinate activity - direct or via regulatory factors)

Mechanical coupling (motor influenced by forces from opposite polarity motor)

Question 3

How do melanosomes move in mammalian cells?

Answer 3

Use kinesins and dyneins for long distance travel to elk periphery and onto neighbouring keratinocytes or photoreceptors

Question 4

What happens to melanosomes at the periphery?

Answer 4

Use myosin to navigate actin barrier.

Question 5

How do fish change colour?

Answer 5

Pigment granules move along MTs

When intercellular cAMP decreases kinesin inactivated –> dyneins free to drag pigment toward cell enter and change fish colour

(Dynein and kinesin associated with pigment granules)

Question 6

How do Golgi and mitochondria move?

Answer 6

Scatters if MYs disrupted or dynein knocked down by p50

Knockdown of kinesin 1 decreases movement.

Question 7

What is the speed of muscle myosin on an in vitro assay?

Answer 7

4.5 MM/sec

Question 8

What does the crystal structure of kinesin 1 show?

Answer 8

It is auto-inhibited

Dimer if tail folded back and one monomer in between pair of heads.

Question 9

How else can kinesin 1 be regulated?

Answer 9

Binding partners - FEZ1 can release auto-inhibition.

Phosphorylation - of inhibitory tail domain of certain kinesin - 7’s by kinases e.g. CDK1 relieve auto-inhibition