Cytoskeleton II

Question 1

Cyto skeleton motor dependent types

Answer 1

Motor driven or polymerization-driven

Intracellular transport-motor-driven or polymerization-driven

Ciliar/flagellar beating

Question 2

What makes up contractile ring/what is its function

Answer 2

Actin and myosin filaments

Used to cleave the cell in two

Question 3

How does city skeleton drive morphogenesis

Answer 3

Invagination of epithelial sheet is caused by organized tightening of adhesion belts
-associated with actin filaments/myosin II

Question 4

Traffic direction

Answer 4

Both ways on actin and MT

Question 5

3 classes of cytoskeletal motors

Answer 5

Myosins-move along actin filaments

Dyneins/kinesins-move along Mts
(dynein is much bigger)

All three classes are ATP ases and have multiple isomforms encoded by multiple ones

Question 6

Molecular motor facts (5)

Answer 6

All atpases

Related structure and mechs-large gene families

Partiulular isoform moves in one direction

Vesiceles/organelles move on microtubules and actin filaments + more than one kind of motor

Downstream targets of cellular signalling cascades

Question 7

Molecular motor energetics

Answer 7

Energy from ATP hydrolysis-causes conformational change

-tension or moments is generated along filament or MT

Question 8

Myosin facts

Answer 8

Large gene family

Two heavy chains, tw or more light chains

Most move toward plus direction

Globular head with Atlases

Tail is variable domain-coiled coil for dimerization and/or binds to membrane or target vesicle

Classification based on motor domain

Mutations-result in inherited human diseases

Question 9

Kinesin facts

Answer 9

Motor domain (head)-heavy chains contain ATPase and MT binding site

• N terminal is plus end directed
• C terminal is minus end directed

Kinesin 1C is bound to tail

Neckregion determines opolarity
Stalk is coiled for dimerization

Tail binds to varaible target and to light chains

Question 10

Dyenin facts

Answer 10

Minus end directed

Big

AAA proteins (ATPase associated with diverse cellular activities)
-energy from hydrolysis, conformationatal change, work

In cilia/flagella

From periphery of cell to nucleus

Can see in EM as little spur

When has ATP bounds attached to microtubule
-lose P and released

Question 11

Karatagener syndrome

Answer 11

Primary ciliary dyskinesia

Resp tract infections/male infertility

Mislocalized dyenin-stuck in basal body

Cilia are immotile-mutation is in outer arm ciliary dyne heavy chain, outer arms mmissing

Question 12

How do cytoskeletal motors work

Answer 12

ATP energy to mechanical work and heat
-conformational change

rate limiting step is Phosphate release following hydrolysis

• binding to actin or microtubules accelerates rate limiting step
• actin/MT is nucleotide exchange factor

Kinesin and myosin differ in processivity

Question 13

Myosin II firing

Answer 13

Add ATP- conformational change and release, before hydrolysis

• add ATP-release from actin
• recovery stroke occurs

Release ATp-rebind-actin speeds up, power stroke-rigor mortis–stuck on-actin

Question 14

What determines myosin speed

Answer 14

rate of myosin ATPase

Question 15

How reg function of myosin

Answer 15

OM (drug)-binds to cardiac myosin, increases contractility bu accelerating Phospaht erelease-accelerating transition to strong bind and icnreaesd force

Question 16

Kinesin firing

Answer 16

Bind of ATP weakens affinity for MT

P lease-binds with higher affinity

MT binding accelerates product release and conversion from weak to strong binding (power stroke)

Question 17

Power stroke

Answer 17

Conversion of weak to strong binding

Question 18

Kinesan walking

Answer 18

Trai]ling head has ADP and weakly associates wit hMT

ATP head bond to MT

They switch when ATP is hydrolyzed and adde

Question 19

Motor, substrate track and direction of movement

Answer 19

Myo-ATP-actin-Plus end (mostly)

Kinesan-ATP-MT-Plus end (mostly)

Dyenin-ATP-MT-Minus end

Question 20

Localization of motors

Answer 20

Tail determins localization
-bind to specific targets

head determines classifcatio/identity/motor function

Antibodies also allow localization of myosin and kinesin isoforms

Question 21

What is between motor and cargo

Answer 21

Sometimes many proteins that allow great increase of specificity and regulation
-scaffoleer, adaptor, direct bind etc.

Question 22

Dynactin

Answer 22

Multifunctional protein complex that increases precocity of dyenin-helps bind to MT and other proteins

Binds to tail of dyeing

Has many parters including spectrin that help binding

Question 23

Which way does traffic go on MT’s and actin

Answer 23

Both ways-can be short or long

Question 24

Intracellular transport facts

Answer 24

many things are transported from ER to cell periphery and back

Transport can occur on _ end of MT as MT grows

Vesicles/organleles can have more than one molecular motor=can travel on both MT and actin

Question 25

Transport of pigment granulaes

Answer 25

Pigment is in melanosome vesiceles
(melanocytes-cells that make pigment)

Redistribution requires transport on MT and actin filaments

Melanocytes are from neural crest cells

Myosin 5-if don’t have won’t have normal pigmentation

Question 26

Myosin V

Answer 26

Binds to carbgo via melanophilin and RabGTPs

Need entire thing to move melaosomes

Myosin 5 attaches from actin to the melanosome

Question 27

Ras GTPases

Answer 27

target myosin to specific intracellular membranes

if defeiceint-cant target to specific area-cluster in areas where they shouldn’t be

Question 28

Griscelli type 1

Answer 28

elejalde syndrome

Silvery hair, light skin in child of dark skinned parents

neuro defects

Bigpment clumped in hair and not distributed as in normal hair

Malosomes stunch in basal ep-not anywhere else