Lecture 9 - Mitochondria 3 Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

What are the components of the SAM complex?

A

Sam50 and Mdm10 are beta barrel proteins.

Sam 35 and 37 are receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the function of the SAM complex?

A

SAM complex is a machinery dedicated to synthesizing beta barrel proteins and is found in outer membrane of the mtichondria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the equivalent of SAM50 in bacteria?

A

OMP85

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How important is the beta barrel pathway for living organisms?

A

the pathway through which beta barrel proteins enter outer mitochiondrial membrane has been conserved. Beta barrel proteins enter through TOM complexes and then are translocated via SAM complex into the outer membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How are beta barrel proteins incorporated into the outer membrane of mitochondria?

A

Beta barrel proteins form intermediate structures before being incorporated into outer membrane. These structures. beta barrel proteins interact with chaperones which carry them (they are hydrophobic which necessitates the use of these chaperones) to the SAM complex before being incorporated into the complexes. THe whole complex is often formed by various methods of transport.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the compenents of the beta-signal?

A

xxx Po x G xx Hy x Hy x

Any variation in these amino acid would prevent interaction of beta barrel proteins with the SAM complex.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Where do outer membrane protiens interact with the SAM complex?

A

Interaction site is at the C-terminus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Are all outer membrane proteins beta barrel proteins?

A

No, many are made up of alpha helical transmembrane domains.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the types of protein present in the outer membrane of the mitochondria?

A

N anchored

C anchored

Some proteins have an anchor at one terminus that extends so much that the middle of the protein appears to be in the membrane. (example of this is Tom22)

Some proteins penetrate the membrane at multiple locations. (eg Fzo1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Name some C-tail anchored proteins in outer emmberane of mitochondria:

A

Tom 5,6,7

Bak

Bcl-2

Fis - 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the typical structure of C-tail anchored proteins?

A

Cytosolic domain

TMD (anchor region)

C-tail

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Where does the specificity of C-tail anchored proteins come from?

A

TMD

C-tail

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How is the target of a C-tail anchored protein determined?

A

hydrophobicity of anchor

net charge of C-tail

length of the anchor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the proteins responsible for insertion of protiens into the ER membrane?

A

GET proteins are required for tail anchored protein import into the ER.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the steps of the GET pathway?

A

1) GET3 receives tail anchored protein.
2) GET3 enters close conformation and is targetted to the ER membrane where it is received by GET1 and GET2 and inserted into the membrane.
3) GET3 re-enters open conformatino and can receive more tail anchored proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is a significant difference between ER and mitochondrial transmembrane proteins? Why are these difference significant?

A

ER transmembrane proteins have longer transmembrane domains than mitochondrial ones.

Positively charged C-tails in mitochondrial tail anchored proteins whereas negatively charged in ER tail-anchored proteins.

THis is significant because GET3 has a long-positively charged groove. This means that Mitochondrial transmembrane protein tails get repulsed from the groove and are also too short to fit into the groove.

17
Q

How are tail anchored proteins trafficked to the peroxisomes?

A

Tail anchored proteins that go into peroxisomes first enter the ER membrane then peroxisomes.

18
Q

How are tail anchored proteins targetted to the mitochondria?

A

When GET pathway proteins are mutated then the tail anchored proteins go by default into the mitochondria’s outer membrane. As a result the Msp1 degrades them and so only functional mitochondrial tail anchored proteins end up in the mitochondrial membrane.

19
Q

What is Msp1?

A

A mitochondrial outer membrane AAA-ATPase protein that breaks down mistargetted C-tail anchored proteins.

20
Q

What does the ATPase domain of Msp1 look like?

A

Single ATPase domain composed of canonical walker A and B motif

21
Q

What is the function of Mim1?

A

Mim1 acts as an insertase for N-terminal anchor proteins.

22
Q

What proteins use Mim1 for entry into the outer membrane?

A

N-tail anchored proteins such as:

Tom70

Tom20

OM45

Multipass membrane proteins with the N terminus outside and C-terminus in the intermembrane space (eg Ugo1)

23
Q

What proteins use the SAM complex for entry into outer membrane?

A

Beta barrel proteins

C-tail anchor proteins with long intermembrane space of mitochondria.