Intracellular Compartments and Protein Sorting 2

Question 1

What are most mitochondrial proteins encoded in?

Answer 1

nuclear DNA, although some made in mitochondria

Question 2

Mitochondrial proteins are ______ on ribosomes and _______ into mitochondria

Answer 2

synthesized

imported

Question 3

Proteins need to ______ outer and/or inner mitochondrial membranes through _________

Answer 3

cross, translocation

Question 4

What directs proteins to correct compartment in mitochondria?

Answer 4

signal sequences

Question 5

Where are mitochondrial signal sequences located?

Answer 5

N terminal and internal

Question 6

_______ charged residues cluster on one end and ________ _______ on other end to form an ________ alpha helix

Answer 6

positively; uncharged hydrophobic; amphiphilic

Question 7

For mitochondrial signal sequences what doe receptor proteins recognize instead of the precise sequence?

Answer 7

the configuration

Question 8

On mitochondrial signal sequences, multi subunit protein complexes called ______ mediate translocation

Answer 8

protein translocators

Question 9

Describe translocase of the outer membrane (TOM)

Answer 9

present in outer membrane
required for import of all nuclear encoded proteins
inserts them in outer membrane

Question 10

Where is translocase of the inner membrane (TIM) located?

Answer 10

inner membrane

Question 11

What are the two TIM complexes?

Answer 11

TIM22 TIM23

Question 12

What does TIM 23 do?

Answer 12

transports soluble proteins into matrix and helps insert membrane proteins in inner matrix

Question 13

What does TIM 22 do?

Answer 13

mediates the insertion of specific subclass of proteins

Question 14

What are the two components of TOM and TIM complexes?

Answer 14

receptors for mitochondrial precursor proteins

translocation channels

Question 15

What does Sorting and Assembly Machinery (SAM) complexes do?

Answer 15

translocate and inserts/folds beta barrel proteins in the outer membrane

Question 16

What does the OXA complex do?

Answer 16

mediates insertion of proteins synthesized in mitochondria

Question 17

Precursor proteins entering mitochondria are folder or unfolded?

Answer 17

unfolded

Question 18

How is the unfolding of precursor proteins maintained?

Answer 18

through interactions with chaperone proteins (cytosolic Hsp 70 family)

Question 19

import receptors of ______ complex bind signal sequence of incoming proteins

Answer 19

TOM

Question 20

chaperone proteins are ____ and unfolded protein is fed–signal sequence first into _____ channel

Answer 20

stripped off; translocation

Question 21

TOM transport protein across the outer membrane to where?

Answer 21

inner membrane space

Question 22

When a protein binds to TIM complex it moves through channel to where?

Answer 22

matrix

Question 23

What are signal sequences cleaved off by?

Answer 23

peptidase

Question 24

Transport through TIM depends on ______

Answer 24

membrane potential

Question 25

What helps in folding of imported protein using ATP?

Answer 25

HSP 60

Question 26

What is the ER membrane continuous with?

Answer 26

nuclear membrane

Question 27

What is the internal space of the ER called?

Answer 27

ER lumen

Question 28

ER signal sequences vary in _____ ______ sequence

Answer 28

amino acid

Question 29

ER signal sequences have how many non polar amino acids at its center?

Answer 29

8 or more

Question 30

What two components guid ER signal sequence to ER membrane?

Answer 30

signal recognition particle (SRP)

SRP receptor

Question 31

What is the SRP made of?

Answer 31

6 different polypeptides bound to a single small RNA molecule

Question 32

The SRP is rod shaped with large _______ lined by ______

Answer 32

hydrophobic pocket; methionine