cytoskelton actin

Which filaments are from cell movement and which for intracellular transport?

Actrin is whole cell movement and intracellular

Microtubules are for intracellular

Which have a globular enzymatic subuinint? And which fibrous? Whiare are polar

Microtubulus and actin are polar whit a globular ASSYMETRIC subuint

Intermidiate filaments are apolar and have a fibrous sub.

In the epithelaila tissue how are in the different layers organized cytoskelteon elements

1. Actin is in the APICAL PART with. MICROVILLI

2. Actin is also in the apical part makind FASCIA ADHERENS connecting cells to cell

3. Then there iss for anchorage intermidiate filament for desmossomes

4. In tha BASAL PART extending vertically microtubules to coordinate and have intracellular transport of newly synthtized things

What strcuture asisst in the polymerization of actin

A loing microtubule that extends from mtoc

The actin subuint G is formed by ?

How many isoform are there of actin in vertebrates?

Describe the polar ends of f actin

Globular actin each is 375 AA

Atp

3 isoform alpha muscle cell beta gamma non muscle cell

G sub. Assemble for F ( filamentous)

The + END IS BARBERED

- minus is pointed

Which kind of actin has graetr affinoty of the f actin?

What is TREADMILLING AT STEADY STATE and how does it allowsmovement along the filament

Is adding or subtracting the subunit at a different rate?

ATP actin which is more present than adp actin

Atp actin binds to the plus end, after hydrolisis adp actin oi slees thight so dissociated from the - end.

Tradmilling: You add at the plus end subuint as atp actin has more affinity and you leave sub. At the - end when adp actin dissociates after hyrodlisis.

OVERALL YOU HAVE THE SAME LENGHT ( add and leave happen also at the same rate)

Nucleation

What is the critical concentration?

When does the cell gorw and when does it swrink

If the concentration is at equilirbium what do you have

The critical concentration is the sub. Grow and sub. Shrink balancing

If it is more than critical : grow

Less shrink

Equal: treadmilling

If c actin is more than cc?

C actin is less than cc

Cc(atp-actin) is less than actin and less of adp actin?

C actin more than cc you have addining of atp actin at both ends

C actin is less than cc you loose 8 SWRINK

If cc atp actin is less than the concentration of actin and of adp actin you are in a treadmill

Which is the effect of CYTOCHALSIN BAND LATRUNCULIN Drugs

F actin disappears beacuse depolym. Prevails

What is the effect of phalloidin

F actin fixed in existing patter ( used to stain f actin in dead cells)

When the concentration of actin is lower than the cc of the plus end what does happen

CC ACTIN MENO CC+ END SWRINK!

Which are the function of profilin and tymyosin?

PROFILIN binds adp actin and promotoes echange from atp PROMOTES POLYM.

Tymoyosin inhibits pilymerization

Which is the role of fomins and arp 2/3 complex?

FORMIN binds ATP actin and nucleate initial polymerization of UNBRANCHED actin gfilaments

Arp2/3 initiate growth of BRANCHED actin filaments

In affecting the protein stability which are the role of

1. Tropoomyosin

2. 2. Capping proteins

3. Cofillin?

tropomyosin stabilizes actin and binds ALONG THE LENGHT

Capping protein both can be at + or minus

COFILLIN taglia i filamenti e genera cosi nuove + o - end

Which protein severs the filaments generating new ends

Cofilin

Does profilin bind atp or adp actin

Profilin binds adp and promotes change from adp to atp

What is the role of tropomodulin

It prevents assembly and DIASSEMBLY AT THE MIUS END

Gelsolin function

Severes filament as cofiin but it binds at the PLUS END

Does cofilin accelerate assembly or diassembly?

Diassembly by severing

Which protein aid in attaching actin to the membrne

Spectrin

Which are the protein that allow bunding and croo linking

Fimbrin and filamin

How does actin appear in stress fibers?

In the cell cortex?

In lamellipodiim?

In filipodium?

In stress fibers contractile bundles!

In the cell cortex in GEL LILE NETWORK

In lamellipodium os dentritic network

In filopodium is TIGHT PWARRELEL BUNDLES

How does actin appear in filopodia

Thin parallel bundles tightly oacked and is associated with FIBRIN

What is the difference in the arrangement between filopodia and stress fibers

In filopodia they are very packed also with fibir in parallel bundles TO NOT ALLOW MYOSIN to enter

In stress bunles they are in contractile bundles allowing myosin

Where is actin in a gel like network?

Which protein is essential in to form the network in erytrocytes?

In cortical actin as in ERYTROCYTES!

Spectrin is a tetramer protein that allows this gel linke netwrok with actin

Ankyrin is a protein that links thos complex to the plamsa membrane

What is ankyrin?

What is the function of protein 4.1

Protein to link the actin spectric complex to the pm in erytrocytes

PROETIN 4.1 lins spectrin actin to glycoporin

What disease is associated to a disconnection of CORTICAL ACTIN netwrok?

Musclar dystrophy

What is the role of dystrophin

Dystrophin in muscle cell links theACTIN to protein in PLASMA MEMBRANE that link to the ECM

Helping to mantain stability in the contraction

What happens if sytrophin is absent or abnormal

Dystrophin links actin to pm so if it absnent dystrophy of duchenne

If abnormal becker

Microvilli have what conformation of actin?

As in filopodia there are pararllel bundles of actin

PARALLEL BUNDLES of 20-30 actin filaments

THAT ARE LINKED WITH fibrin and villin

Ehat link toghter the filaments in microvilli?

What links the actin bundles to the pm

FIMBRIN AND VILLIN

CALMODULIN AND MYOSIN I link the bundles to pm

Which protrusion are supproted by actin and what are their functions

1. Psuropdia: hagocytosis

2. Lamellipodia: actinis branched and are sheet like at the leading edge of moving cells

3. Filopdia where actin is in parallel bundles and it serves as a to expolore the enviroment

What role does actin have in platelts activation?

Platelets when activated reorganize actin changing its form from DISCOID to SPERICAL to filo and lamellipodia( sheet linke) and finally a spread platelts

What is myosin?

What is the role of the head of myosin?

Describe the structure of myosin

Which type can form filaments

Myosin is an actin dpendent motor protein

Its head bins actin and can hyrdolise atp

Mysoin II has a long tail and can assemble into filaments allowing contraction also in non muscle cells

The strictire is a GLOBULAR HEAD REGION. A light and heavy chain

The chains in the tail are in a apha helix

How is the tail arranged and how is the head of myosin

Head is globular

Tail is an aplha chain of the heavy and light

Does myosin. Always move towards the plus end of actin?

NO MYOSIN 6 MOVES TOWARDS THE MINUS END

In muscle cell what type of myosin do i find

Myosin 2 which has the capacity to form thick filaments

Which kind of myosin are involved in organelle movements and vescile traffick

Myosin I and 5

In the sarcomere

A band

I

H

Which does not change’ which disappears

What happens at the m line

A band is myosin

I band is Actin only

H only myosin ( hate myosin and I love actin)

In the M line myosin changes orientationb and POLARITY OF ACTIN REVERSES

What is the z disc

The z is where the + end of actin links

As there is contracion and filaments slide Which bands changes

Z disc come closer toghter

A does not change ( the one with mysoin)

H (the oine with only myosin ) and I ( the one with only actin) almost disappear

When atp binds does myosin aggregate or fdissociates

Atp bind make myosin head dissociates

When atp is hysolized myosin changes conformation

As p exists myosin binds actin in a new position

As ADP exits myosin returns yo its orignial position and the actin filaments slide and you have contraction

Once atp is hydrolized into adp and p when does the actin filaments slide

When p exist myosin binds in a new site

When adp exist the filaments slide

In skeletal muscle when calcium is releades from the SR what does it bind

Troponin C that makes tropmyosin move from the actin binding site

Hoe does smooth muscle contraction work

Gpcr, plk, ip3, calcium calmodulin, phophorylation of mlck

Phophorylated myosin binds actin

IN SMOOTH MUSCLE THERE IS NO TROPONIN

What myosin allows contraction even in non muslce cels and how does it work

Myosin II

The contraction in non muscle cells workds link in smooth muscle ( phophrylation of mlck

Which myosin are not involved in contractions

I and V for vescicle trafficking and cell movement