Intracellular Compartments And Protein Sorting 2

Question 1

Movement of proteins into the mitochondria is called ______

Answer 1

Translocation

Question 2

______ direct proteins to correct compartment in mitochondria

Answer 2

Signal Sequences

Question 3

Mitochondrial Signal sequences

Answer 3

• N-terminal and internal signal sequences
• Positively charged residues cluster on one end and hydrophobic on the other end of the helix
  ( note that specific receptor proteins recognize this configuration rather than precise sequence)

Question 4

Multi-subunit protein complexes called ______ mediate translocation (movement of protein into mitochondria)

Answer 4

Protein translocators

Question 5

Translocase of the outer membrane (TOM) is present in the ______ membrane

Answer 5

Outer

Question 6

Which Translocase is required for import of all nuclear encoded proteins into the mitochondrial membranes

Answer 6

Translocase of the outer membrane (TOM)

Question 7

Translocase of the inner membrane (TIM) is present in what membrane

Answer 7

Both outer and inner membrane

Question 8

Most mitochondrial proteins are encoded in _____. Synthesized on ____ and _____

Answer 8

Nuclear DNA, synthesized on ribosome and imported into mitochondria

Question 9

What are the two TIM complexes

Answer 9

TIM 22 and TIM23

Question 10

TIM23 transports _____ and helps insert membrane proteins _______

Answer 10

soluble protein into matrix, in inner membrane

Question 11

TIM 22 mediates the insertion of _____

Answer 11

a specific subclass of proteins (e.g. ATP, ADP and Pi transporter)

Question 12

TOM and TIM complexes have 2 components

Answer 12

• Receptors for mitochondrial precursor proteins

- Translocation channels

Question 13

SAM complex (sorting and assembly machinery)

Answer 13

• Translocates and inserts/folds beta barrel proteins in the outer membrane

Question 14

OXA complex

Answer 14

• Mediates insertion of proteins synthesized in mitochondria

Question 15

What are the translocators in the mitochondrial membranes

Answer 15

• TOM and TIM complexes
• SAM complex
• OXA complex

Question 16

Precursor proteins enter the mitochondria are ____

Answer 16

unfolded

Question 17

The unfolding of precursor mitochondrial proteins is maintained by interactions with

Answer 17

chaperone proteins (cytosolic Hsp 70 family)

Question 18

Import receptors of TOM complex bind _____ of incoming protein. Then chaperone proteins are ____ and unfolded protein is fed- _____ first into the transaction channel

Answer 18

signal sequence, stripped off, signal sequence

Question 19

TOM transports protein across the outer membrane to the _______. Then protein binds to _____ complex and moves through channel to matrix and then the signal sequence is cleaved off by

Answer 19

inner membrane space, TIM complex, peptidase

Question 20

Bound Hsp 70 dissociate from precursor mitochondrial at expense of

Answer 20

ATP hydrolysis outside the mitochondria

Question 21

After passing through TOM, protein interacts with TIM and transport through TIM depends upon _____

Answer 21

membrane potential

Question 22

Energy in electrochemical gradient drives translocation of positively charged sequence through TIM by _____

Answer 22

electrophoresis

Question 23

______ bound to TIM23 on matrix side and pulls protein into matrix space

Answer 23

Mitochondrial Hsp 70

Question 24

The release of protein, by Hsp70, in the matrix space is an

Answer 24

ATP dependent step

Question 25

____ helps in folding of imported mitochondrial protein using ATP

Answer 25

Hsp60

Question 26

import of mitochondrial proteins into the outer membrane

Answer 26

• Pass through TOM complex and enter inter-membrane space
• Bind to chaperone proteins
• Then bind to SAM complex in outer membrane
• SAM inserts and folds them in outer membrane (ex. porins(beta barrel proteins))

Question 27

ER is organized into a network of _______ and ____

Answer 27

branching tubules and sacs

Question 28

ER membrane continuous with ______

Answer 28

nuclear membrane

Question 29

Internal space of ER called ______

Answer 29

ER lumen

Question 30

ER plays central role in ___ and ____

Answer 30

protein and lipid synthesis

Question 31

What is the site of production of all TM proteins

Answer 31

ER

Question 32

What is co-translation

Answer 32

The ER-bound ribosome forms protein