Microtubules

Question 1

chemical property of microtubules

Answer 1

polarized

Question 2

microtubules oriented with + ends toward:

Answer 2

plasma membrane

Question 3

microtubules oriented with - ends towards:

Answer 3

centrosome

Question 4

4 functions of microtubules:

Answer 4

mitosis, transport, motility, signaling

Question 5

microtubules are composed of these subunits

Answer 5

alpha- and beta- tubulin dimers

Question 6

each MT tubulin monomer can bind:

Answer 6

1 GTP

Question 7

GTP bound to this tubulin is physically trapped at dimer interface and is never hydrolyzed or exchanged

Answer 7

alpha-tubulin

Question 8

tubulin type can bind either GTP or GDP

Answer 8

beta-tubulin

Question 9

one tubulin MT subunit consists of:

Answer 9

tubulin heterodimer

Question 10

tubulin heterodimers assemble linearly to form:

Answer 10

protofilament

Question 11

13 protofilaments form:

Answer 11

microtubule

Question 12

structure of microtubule

Answer 12

hollow tube

Question 13

drug stabilizes MTs

Answer 13

Taxol

Question 14

drug binds and stabilizes actin filaments

Answer 14

Phalloidin

Question 15

drug caps filament plus ends and destabilizes microfilaments

Answer 15

Cytochalasin

Question 16

drug severs actin filaments

Answer 16

Swinholide

Question 17

multiple subunits associating laterally important for allowing cytoskeletal filaments to:

Answer 17

resist breakage

Question 18

for assembly of MTs, tubulin concentration must be:

Answer 18

above Cc

Question 19

for MTs to depolymerize, tubulin concentration must be:

Answer 19

below Cc

Question 20

end that tubulin alpha-beta-dimers add more rapidly

Answer 20

+ end

Question 21

Preferred end for assembly is the (+) end, in which this tubulin is exposed

Answer 21

beta tubulin

Question 22

Cc is lower at this MT end

Answer 22

+ end

Question 23

GTP bound to beta-tubulin hydrolyzes during

Answer 23

polymerization

Question 24

Free energy from hydrolysis is transferred to polymer, making dissociation of this form of tubulin more energetically favorable

Answer 24

D-form

Question 25

soluble tubulin subunits are in this form

Answer 25

D-form

Question 26

MTs have GTP cap at this end

Answer 26

+ end

Question 27

Cc is when:

Answer 27

on rate = off rate

Question 28

this tubulin subunit form has higher affinity for GTP-tubulin

Answer 28

T form

Question 29

this tubulin form has higher Cc

Answer 29

D form

Question 30

dissociation of subunits preffered on this end at intermediate concentration

Answer 30

• end

Question 31

dissociation of tubulin dimers is favored at this end because Cc T is lower than intermediate concentrations

Answer 31

+ end

Question 32

name for MT movement in live cells

Answer 32

treadmilling

Question 33

to visualize treadmilling, small amount of this injected into cell

Answer 33

rhodamine conjugated tubulin

Question 34

describes the assembly, catastrophe, disassembly, and rescue of MTs

Answer 34

dynamic instability

Question 35

dynamic instability depends on:

Answer 35

GTP cap

Question 36

GTP cap removal from + in results in reduced affinity for:

Answer 36

Tubulin-GTP (T form)

Question 37

during this stage of dynamic instability, subunits lost from + end and local tubulin subunit concentration increases

Answer 37

dissasembly

Question 38

during this stage of dynamic instability, free tubulin-GTP reaches Cc of D form

Answer 38

rescue

Question 39

these proteins stabilize MTs

Answer 39

MAPs

Question 40

3 types of MAPs

Answer 40

tau, MAP2, MAP4

Question 41

MAPs bind:

Answer 41

charged wall of MT

Question 42

MAP type found only in dendrites

Answer 42

MAP2

Question 43

MAP type forms fibrous cross-bridges between MTs and links to IFs

Answer 43

MAP2

Question 44

MAP type is present on both dendrites and axons

Answer 44

Tau

Question 45

MAPs are regulated by:

Answer 45

phosphorylation

Question 46

these control MAP activity

Answer 46

MARK/Par-1 and CDK

Question 47

cell with overexpression of this MAP have larger diamer and MTs more spaced apart

Answer 47

MAP2

Question 48

these proteins bind to the + end of MTs

Answer 48

+TIP

Question 49

MT protein binds seam at + end and acts as “weld”

Answer 49

EB1

Question 50

proteins enhance MT catastrophes by enhancing GTP hydrolysis at + end

Answer 50

Op18/Stathmin

Question 51

inactivates Op18/Stathmin

Answer 51

phosphorylation

Question 52

organizes MTs throughout the cell

Answer 52

centrosome

Question 53

centrosome consists of:

Answer 53

two centrioles and pericentriolar material

Question 54

pericentriolar material contains:

Answer 54

gamma-TURC (Tubulin Ring Complex)

Question 55

serves as nucleation site for MT filaments

Answer 55

gamma-TURC

Question 56

centrosome (MTOC) is located at:

Answer 56

center of cell (near nucleus)

Question 57

gamma-TURC located at this end of MT

Answer 57

• end