microtubules and intermediate filaments

What kind of protein is tubulin

Which are the different subuint and which create dynamic instability?

Which is in the centrosome

Is made of globular protein tubulin

Apha tubulin is the one with TRAPPED GTP NOT HYDROLIZED GTP!

Beta is the one that creates instability because gtp is not trapped an dit can change

Gamma tubulin is the one in the centrosome that starts microtubules formaion

Describe the structure if a microtubule

How is polarity here?

1. Microtubule is fromed by 13 protofilaments of tubulin alpha and beta dimers arranged around a hollow core

2. ( 13 dimers di alpha e beta)

3. Alpha is minus end

4. Beta is the plus end

Gtp is bound to which end?

What causes bending in the filament and rapid depolymerization?

Gtp is bound to the plus end gdp minus

When gtp hydolysis occurs the conformational changes make having depolymerization loosing gdp from the minus end

GDP weakens the interaction in the filaments! That bends

When microtubules are stabilized at the mnus end what can rapid gtp hysdrolysis?

Dyanamic instability with cycles of growth and shirnkage

When is the GTP CAP PRESENT

Gtp cap is present in the plsu end if the gtp tubulin is fastere than hydrolized one and it continous to grow.

If the gtp hydrolysis is fatser you lose the cap, gdp in THE PLUS END make sthe microtubule dissassemble anf shrink

When does the micortubule diassemble and shrink

When you lose the can and the hydrolyzed gtp is hyrodlized more and gdp is bound to the plus end!

This is CATOSTROPHE

Which drugs make binding along filaments?

A

Taxol which is used in cancer ttreatment

Microtubules fuction are inhibited also by both POLYMER STABILIZING AS TAXOL AS POLYMERS DESTABILIZINGING drugs

Centrosomes are the initiation sites from microtubule assembly which end is anchored in the centrosome

The minus end is anchored

So the filaments grow outward fromm the centromere

What is the mtoc

The centrosome

Structire of centrosome

Do the centrioles have a role in nucleating mcirotubules?

The centrosome is formed by 2 centrioli

1 centriolo è 9 triplette di microtubules. 9×3

NO CENTRIOLES ARE IMPOARTANT FOE CILIA AND FLAGELLA and the centrosome by replicating andthen organizes the spindles

The one for nucleating microtubules is the gamma ring

Where is the gamma tubulin ring located?

Gamma tubulin It is not in the centrioles but in the pericentriolar material where is associated with other protein in a complex

Are centrioles needed for the microtubuled organization function

NO centrioli are for cilia flagella and mitosis

What changes the stability of microtubules

Post translational modifications to create new binding sites form MBPs ( cell shape and polarity)

What are the effects of polymerase map and depolymerase map

Polyn. Accelerates growth adds gtp tubulin while depoly. Makes gtp tubulin dissociate from the plus end losing its cap and going to catastrophe-

Which is a catatrophe factor?

Which increases stabilization

KINESIN 13 is a catastrophe factor

While MAPS ( XMAPS ECC… stabilze) and induce growth.

What stabilzazer of microtubules you find in axons

Tau associated, alzhemier if bad

Dentrites: microtub. Oriented in both directions MAP2

In the gamma ring the gamma turc is at the plus or minus

Minus

To what do dynesi and kinesins move towards

DYNESIN is retrograde so it moves towards the minus end

KINESIN IS ANTERORETROGRADE MOVING TOWARDS THE PLUS END

While microtubules are gtp depened motor proteins are?

Atp dependendt in fact kinesin are similar to myosins ( evolutionarly similar)

Microtubules are like i binari Tto allow motor proteins to move intracelullarly.

Structure ( similar to mysoin) of kinesins

Plus end terminal is…

Kinesin are similar to myosins so heavy and light chain in apha helix

Plus end terminal is N.

The rare kinesins that move tpwards the minus end have which terminal

C terminal

But the majority are towards the plus with N TERMINAL

Dynesin are related to myosin?

What are the difference between axonemal and cytoplasmtaic ynesin

No

AXOEMAL. CILIA AND FLAGELLA

Cytoplasmatic is for vescicle traffick throught the cytoplasm

Dynasin and kinesin are atp dependendt

To exend to the periphery what does ER use ?

Doe sgolgi utilized dynesin or kinesin to be positioned near the centrosome

What happens to both in case of disruption of mucrotubules

Kinesin fo ER,

Dynesin for golgi to be near the centrsome

Er would go towards the center, GOLI WOULD BREAK INTO VESCILCE

Cilia ad falgella structure

What is the structure of an axoneme

The 2 central microtubules are identical?

Microtubules and axonemal dynesin

Axoneme is 9+2 pattern centernal pair with 9 doublets.

In the doubket one is complete A and one is incomplete B

The two tubules are linked by NEXIN

While dynein attaches to each A tubule

What is the role of nexin

To link inthe axoneme the outer 9 doublets toghter

Cilia and flagella are made of microtubules and dynesin now, to what are the microtubules minus end anchored to?

The minus end of mcrotubule is anchored to the basal body which is similar to centrioles (( 9 triplets)

What is the function of basal bodies?

Is the final region where the minus end is anchored and it is also INITAITED THE AXONEMAL growth

What nucleates the axonemal microtubule

The basal body

What is the movement of cilia due to

The sliding of the doublets 9 microtubules against one onthere in the axoneme

As the cell enters mitosis which microtubule diassambly and wrinkles and which increase

The intermediate microtubules diassemble while the NUMBER of MICROTUBULES EMANATING FROM THE CENTROSOME INCREASES

What are the function of the follwing microtubules

1. KINETOCHORE MICROTUBULESD attche cromosome to centromeres( che non e il centrosome del mtco )

2. CHROMOSOMAL micrtoubules attach the ends of chromosomes with CHROMOKINESIN

3. POLAR are not attched to chromosomes but stabilze by overlapping with each oter

4. ASTRAL microtubule have the plus end anchored in the cell cortex and extend outfors

Astral go from the centosome to the cell surface to position the spindel

What do kinetochore microtub.

Stabilize the chromosomes by linking theirs centromeres

How are the ends of chromosomes connected

By chromsomal microt. Via CHROMOKINESIN

chromosomal movement in anaphase a Is driven by dinesin or kinesin?

Chromosome move towards the spindle poles along the kinetochrore microtubules driven by KINESIN that depolymerizes the tubules.

In anaphase b how

are the spindle poles separate

What do kinesin due?

1. The overlapping polar microt. Elongate and PUSH the spindle poles apart

2. Kinesin brings toward the plus end the polar microtubules

3. Spindle poles are PULLED appart by ASTRAL microtubules

4. Dyneisn moves along the astral mixrotubules towards the MINUS end

5. Astral microtubulus schrinkage

6. Separation of the poles

During the separation of the poles

Which motor protein pulls the overlapping interpolar pushing the spindle apprt?

Which push the astral microtubules

Interpolar are push towards the plus end by kinesin

Astral by dyniesin

Which motor portein moves the chromosomes towards the spindle poles along kinetecores

KINESIS

What function do intermediate filaments have

Are they polar

Are they involved in movement?

Ex. In lamin what can make them assmebly or diassembly

SCAFFOLD for localization of cell process , MECCHANICAL SUPPORT AND STRENGHT

Non polar

FIBORUS SYMMETRIC SUBUNIT

Not involved in movement

Pohophrlation

What kind do you find in muscel cell?

Desmin

What kind do you find in epithelial cells

KERATIN I acidic

II basic

HOW DO INTERMEDIATE FILAMENT organzie the internals tructure of the cell

By extending from around the nucleys to the plasma membrane

What is the role of PLECTIN

PLECTIN ALLOWS TO CONNECT IN. FILAM. TO MICROTUBULES increasing stabiltiy