Intracellular Fibrillar Proteins Self-study

Question 1

Actin

Answer 1

Polymerizing globular subunits (G-actin) to long polymers builds microfilament (fibrillar or F-actin) modulating cell shape and drives cell locomotion

Question 2

Myosin

Answer 2

Motor protein which works with actin to convert chemical energy (ATP) to mechanical work (skeletal muscles). Contains head (binds to actin) and coiled coil tail.

Question 3

Microtubule structure

Answer 3

Globular _ and _ tubulin monomer –>dimer–>polymerization

Question 4

Colchicine

Answer 4

Drug that treasts gout. Inhibits action of white blood cells that mediate inflammation caused by precipitation of uric acid in joints by disassembling MTs.

Question 5

Taxol

Answer 5

Anti-cancer drug which blocks cell division by binding to _-tubulin

Question 6

Microtubule functions

Answer 6

Enable cells to change shape, reinforce cytoskeleton, construct cilia and flagella, align to separate chromosomes during mitosis. Oriented tracks to support movement of transport in cell outward or inward (to MTOC) using molecular motor proteins.

Question 7

Kinesins

Answer 7

Anterograde vesicular traffic. Use ATP to move defective organelles out towards periphery of cell (+ end of MT). Two heads that bind MT and tail-opposite end binds cargo.

Question 8

Dyneins

Answer 8

Retrograde vesicular traffic. Use ATP to move cargo in towards interior of cell (- end of MT). Two heads that bind MT and tail-opposite end binds cargo.

Question 9

Keratin

Answer 9

Intermediate filament protein (exclusively structural). Soft keratins make internal body structures and strengthen nuclear envelope, hard keratins make skin, hair, and claws.

Question 10

Keratin structure

Answer 10

Forms coiled coils (dimer of _ helices). Primary structure contains 7 residue repeating units where 1st and 4th are apolar. Nonpolar residues line up along one side of helix and interact with each other, monomers align in anti-parallel fashion. These dimers assemble to multimers and stabilized by disulfide bridges.

Question 11

Epidermolysis bullosa simplex (EBS)

Answer 11

Keratin gene mutation. Cells rupture when subject to normal mechanical stressm visible blisters.