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Molecular 2018 > Lecture 16 > Flashcards

Lecture 16 Flashcards

1
Q

List the 4 accessory proteins that affect actin subunits

A

ARP Complex

Formin

Thymosin

Profilin

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2
Q

Lamellipodia (flat obtrusive cells), and Filopodia (microvilli) are cell surface projections that help move cells over solid substrate. The arrangement of actin that is needed to create these projections is catalyzed by what 2 types of regulating factors?

A

The ARP complex and Formin

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3
Q

The crawling action of a cell is dependent on what?

A

the actin-rich cortex

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4
Q

How to do neutrophils know where to go?

A

they find the source of a bacteria infection by detecting peptides that are derived from bacteria proteins.

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5
Q

When actin filaments are nucleated, where does this occur and what is it mediated by?

A

near the plasma membrane

ARP complex and Formin

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6
Q

Describe the ARP complex activity

A

involved in the nucleation of the minus end (which it remains associated with) of actin filaments in order to allow for elongation from the plus end of actin filaments near the plasma membrane

(growth from the minus end)

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7
Q

Describe Formin’s activity and it’s subunits.

A

nucleates the assembly of “straight and unbranched” actin filaments and remains associated to the plus end of them

Each formin subunit has a binding site for an actin monomer

“forms straight”

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8
Q

What makes up an ACTIVE ARP 2/3 complex?

A

it’s two types, ARP2 and ARP 3

and a necessary activating factor (will not nucleate without this due to masking of ARP2 and ARP3 by other proteins

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9
Q

compare ARP2 and ARP 3 to actin

A

they are 45% identical

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10
Q

Describe what the activating factor does to contribute to the speed of filament nucleation in an ARP complex.

A

it mimics the plus end of the actin filament, which bypasses the rate-limiting step of filament nucleation.

it does this by inducing a conformational change once it binds to the ARP complex

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11
Q

in terms of Listeria, what is ActA and what does it do?

A

it is a surface protein that is presented by bacterial listeria cells and causes local nucleation of actin filaments (these are cross linked)

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12
Q

Describe Cofilin. what does this have to do with “comet tails” in listeria?

A

is a protein that makes branched actin disassemble after they have “force pushed” the listeria cell around

it disassembles the actin filament “comet tails” listeria uses for mobility

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13
Q

When doe the ARP complex work most efficiently? what does this create?

A

when it is bound to the side of a pre-existing actin filament (cross linked) and the branch can grow in a series of repeated 70 degree branches off of the initial filament

this creates a branched web of actin filaments

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14
Q

Lammellipodia (flat obtrusive cells), and Filopodia (microvilli) are cell surface projections that help move cells over solid substrate and the arrangement of actin that is needed to create these projections is catalyzed by what 2 types of regulating factors?

A

The ARP complex and Formin

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15
Q

Describe formin dimers and what they do.

A

2 formin subunits (each with a binding site for an actin monomer) form a dimer that captures 2 actin monomers.

The dimeric complex of actin monomers that formin dimers create, nucleates the formation of new actin filaments and remains associated with the plus as it rapidly grows

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16
Q

Name the accessor proteins that affect actin subunits.

A

ARP Complex

Formin

Thymosin

Profilin

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17
Q

Define Thymosin

A

Binds with actin subunits to put them into a locked state that prevents their assembly by keeping the monomers soluble so that they are readily available (in large numbers) for generating filaments.

“thigh lock?”

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18
Q

Define Profilin

A

binds to actin monomer subunits and exposes the site of actin that binds to the plus end while also binding it’s “whisker” to the plus end of an actin filament.

Once the monomer binds to the plus end of the filament, the profilin falls off and leaves the filament one monomer longer.

“+1 profile you may know”

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19
Q

List the accessory proteins that affect actin filaments

A

Stabilizers
Tropomodulin

Tropomyosin

Capping protein

Disassembly
Cofilin

Gelsolin
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20
Q

Define Tropomodulin

A

prevents assembly/disassembly at the minus end (for the stabilization of long living filaments)

“duels end negatively”

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21
Q

Define Tropomyosin

A

elongated filament that stabilizes filaments by preventing binding with other proteins (key in erythrocyte cytoskeleton)

“tropoMINEosin”

22
Q

Define Capping proteins

A

prevents assembly/disassembly at the plus end of actin filaments by reducing the rate of polymerization/depolymerization

“cap = + style/protection”

23
Q

Define Cofilin

A

(actin depolymerizing factor) Binds to ADP-actin filaments OR monomer subunits and accelerates disassembly by forcing the filament to slightly twist (makes it brittle and easy to disassemble)

Removes the actin comet tail in listeria

“put em in a coffin, dead”

24
Q

Define Gelsolin

A

severs actin filaments and binds to the plus end, which creates smaller filaments that are then available for assembly/disassembly

Depending on the conditions, it helps with assembly/disassembly

“gel when you cut aloe vera”

25
Q

Define Alpha-Actinin

A

“Bundling protein” that cross-links actin filaments into loose bundles while allowing myosin II to enter and make the filaments contractile

“Myosin II is more alpha than Myosin I”

26
Q

Define Fimbrin

A

“Bundling protein” cross-links actin filaments into tight bundles while excluding myosin II

“fimb is in, but myosin II isnt in”

27
Q

Describe the relationship between alpha-actinin and fimbrin

A

they tend to exclude one another bc of their different functions

28
Q

Describe Filamin’s function

A

Forms loose, highly viscous gel-like structures to help the cell slide across surfaces (cant crawl without this) by clamping 2 actin filaments together at a roughly right angle

“fill em in with gel”

29
Q

Describe Spectrin and it’s function

A

Attaches cytoskeleton to membrane and can cause Hereditary spherocytosis (HS) when it occurs in RBC’s (spherical and bursting RBC’s)

“ghost in the membrane/ ghost pale when your RBC’s suck

30
Q

Describe the ERM family and it’s function

A

includes Ezrin, Radixin, and Moesin which all attach the cytoskeleton to membrane by binding one of their binding sites to an actin filament and the other site to a transmembrane protein

“Ezra Rad Homo”

31
Q

When are members of the ERM family active and inactive?

A

Active in their unfolded state

inactive in their folded state

32
Q

Define Stathmin function

A

binds to tubulin subunits and prevents assembly

“stath sticks”

33
Q

Define TIPS function

A

(plus-end tracking proteins) remain associated with growing plus ends of microtubules and can link them to structures such as membranes

“tips are plus what you payed, and the karma sticks with you”

34
Q

Define Gamma-TuRC’s function.

A

(gamma-tubulin ring complex) nucleates assembly and remains associated with the minus end (alpha and beta tubulin are the subunits for microtubules and are NOT involved in the gamma-TuRC complex)

“Turk grows up with tarzan”

35
Q

Describe the gamma-TuRC complex components

A

The complex is formed by accessory proteins and 2 molecules of gamma-tubulin, and serves as a template for creating microtubules

36
Q

Describe the relationship between Centrosomes and gamma-TuRC’s and their arrangement.

A

Centrosomes (major MTOC of the cell) consist of a fibrous centrosome matrix to which gamma-TuRC’s are attached

Microtubules are nucleated at their minus end at the centrosomes, with their plus ends pointing out towards the cell periphery from the centrosome in an astral formation

37
Q

Describe the function of Katanins

A

severs microtubules

“japanese katana”

38
Q

Describe the function of MAPS and include it’s domain(s)

A

(microtubule associated protein) stabilizes tubules by binding along the sides to inhibit catastrophe and enhance growth

Always have 2 domains; one that binds to the microtubule and one projecting outward

39
Q

Describe the function of XMAP215

A

(microtubule associated protein) stabilizes the plus end of tubules to suppress catastrophe and accelerate assembly

“X made good music”

40
Q

Describe the function of Kinesin 13

A

enhances catastrophic disassembly at the plus end by binding to the microtubule ends and lowering the activation energy needed to pry apart the protofilaments that make up the microtubule.

“unlucky 13 pulls apart protofilaments”

41
Q

Describe the function of Plectin

A

cross linking protein that links microtubules to intermediate filaments

“p lectin = protein linker”

42
Q

Describe the function of Tau

A

(a MAP protein) forms closely packed bundles of microtubules by binding to their N and C-termini and it has a short projecting loop

“Tau is tightly packed, its N-Cane (insane)”

43
Q

Describe the function of MAP2

A

forms widely spaced, stable bundles of microtubules by binding to them with it’s 2 microtubule-binding domains, one of which is on it’s a long projecting domain

“MAP2 has 2 domains, and maps travel far (widely spaced)”

44
Q

Microtubules use _______ to move along _______ or _______ filaments.

A

ATP hydrolysis ; Microtubule ; Actin

45
Q

List the 2 motor proteins that hydrolyze ATP to move cargo

A

Kinesins and dyneins

46
Q

Describe Kinesins

A

most common motor proteins that have their motor domain on the N-terminus of the heavy chain, and walk toward the plus end of the microtubule or “Anterograde”.

These carry a binding site in the tail for a membrane-enclosed organelle

“CommoN kinesins are positive”

47
Q

Describe Dyneins

A

the largest and fastest known molecular motor protein that is composed of 2 or 3 heavy chains (including the motor domain) and walks towards the minus end of the microtubule or “retrograde”.

“Dynein dinosaurs (big, fast, negative)”

48
Q

Compare and contrast the 2 types of dyneins

A

Cytoplasmic dyneins are involved in vesicle trafficking and localization of the golgi apparatus

Axonemal dyneins are specialized for rapid and efficient sliding movements of the microtubule (like in the beating of cilia/flagella)

49
Q

describe the functions of the motor domain and tail domain of motor proteins

A

The motor domain (head) uses ATP to determine the identity of the filament track it will use and the direction it will go, while the tail determines the identity of the cargo

50
Q

What type of process is used to endocytose macromolecules, such as cholesterol?

A

receptor mediated endocytosis

Molecular 2018 (39 decks)

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