L4: Microtubule motor proteins and IMFs

Question 1

What directionality do the two types of motor protein have?

Answer 1

Kinesins are anteretrograde, dyneins are retrograde

Question 2

Main domains of kinesin with function

Answer 2

Head domain (motor that generates movement), neck (flexible, determines direction)

Question 3

Kinesin 1 vs 5

Answer 3

Kinesin 5 is bipolar (2 globular bulbous regions where antibodies bind)

Question 4

Cytosolic dyneins

Answer 4

Retrograde, have an ATPase domain and a MT binding domain. Linked to their cargos (vesicles/chromosomes) by dynactin complexes.

Question 5

How would a cargo change direction?

Answer 5

Able to interact with a different type of motor proteinh

Question 6

How fast do kinesins travel?

Answer 6

600nm/s

Question 7

Structure of cilia and flagella

Answer 7

Axoneme (core), with 9 outer doublet MTs and 2 central pair. Outer doublet MTs have 13-protofilament and 10-protofilament

Question 8

How do C + F move?

Answer 8

Axonemal dyneins generate force by sliding outer doublet MTs past each other causing bending due to constraints by nexin crosslinks

Question 9

Directionality of MTs in mitosis?

Answer 9

(-) end associates with spindle poles for all types

Question 10

Kinetochore MTs

Answer 10

Connect chromosomes by kinetochore attachment site to spindle pole

Question 11

Polar MTs

Answer 11

Hold and control distance between poles

Question 12

Astral MTs

Answer 12

Radiate towards cortex of cell; help position spindle and determine plane of cytokinesis

Question 13

Compare IMF with MTs

Answer 13

IMFs are less dynamic, unpolarized, have no motors, more stable. Therefore used for cell and tissue strength and integrity

Question 14

Class 1 IMFs (protein, distribution, function)

Answer 14

Made of acidic keratins, found in epithelial cells, provide tissue strength and integrity

Question 15

Class 2 IMFs (protein, distribution, function)

Answer 15

Made of basic keratins, found in epithelial cells, provide tissue strength and integrity

Question 16

Class 3 IMFs (protein, distribution, function)

Answer 16

Made of desmin, GFAP, vimentin, found in muscle/glial/mesenchymal cells, provide sarcomere organization

Question 17

Class 4 IMFs (protein, distribution, function)

Answer 17

Made of neurofilaments, found in neurons, provide axon organization

Question 18

Class 5 IFs (protein, distribution, function)

Answer 18

Made of lamins, found in nuclei, provide nuclear structure and organization

Question 19

Why are IMFs stable?

Answer 19

Due to alpha-helical rod structure, overlap along long axis to provide a rope-like filament

Question 20

Basic IMF structure

Answer 20

10nm diameter, globular N- and C-terminal domains joined by central alpha-helical core/rod domain

Question 21

IFAPs (with example)

Answer 21

Intermediate filament associated proteins which connect IFs together and to MTs, eg Plakin

Question 22

Application of IMFs

Answer 22

Tissue specific so make good markers for cell types (eg Stem Cells)

Question 23

Epidermolysis Bullosa

Answer 23

Caused by mutation in Keratin 14 gene