2.2 - Organelle + Gated Transport

Question 1

Hsc

Answer 1

cytosolic chaperone protein

- maintains proteins that have been translate with cytosolic ribosomes in unfolded state

Question 2

TOM 20/22

Answer 2

import receptor

Question 3

what drives import into the mitochondrial matrix

Answer 3

mitochondrial matrix Hsc70 (chaperone protein) and ATP hydrolysis

Question 4

what are contact sites

Answer 4

areas where the mitochondrial outer and inner membrane are close to each other

Question 5

TOM

Answer 5

import receptor and translocator for mitochondrial outer membrane

Question 6

TIM

Answer 6

imporer translocator for mitochondrial inner membrane

Question 7

mitochondrial targeting sequence chemical characteristics

Answer 7

moderately amphipathic

Question 8

what is the mitochondrial targeting sequence recognized by

Answer 8

protein-protein interaction by a signal receptor on the TOM complex

Question 9

how does TOM complex integrate porins into the lipid bilayer from the outside

Answer 9

it doesn’t, can’t integrate porins into the lipid bilayer from the outside directly

Question 10

how are porins integrated into the mitochondrial outer membrane

Answer 10

1) porins first transported into intermembrane space
2) binding to specialized chaperones
3) porins bind to SAM complex
4) SAM complex inserts them into outer membrane

Question 11

BAM

Answer 11

similar to SAM complex, bacterial outer membrane that inserts b-barrel proteins into bacterial outer membrane in gram-negative bacteria

Question 12

what is one piece of evidence that supports the endosymbiotic origin of mitochondria

Answer 12

the central subunit of the SAM complex is homologous to the BAM complex in bacteria

Question 13

translocation method for chloroplast proteins

Answer 13

post-translation translocation

Question 14

compare the import signal sequence of chloroplast to that of mitochondria

Answer 14

similar

Question 15

TOC

Answer 15

import receptor and translocator for chloroplast outer membrane

Question 16

TIC

Answer 16

import receptor and translocator for chloroplast inner membrane

Question 17

where is the photosynthetic system located in chloroplast

Answer 17

thylakoid membrane

Question 18

what is the thylakoid signal sequence located relative to the chloroplast signal sequence

Answer 18

located after

Question 19

transport of thylakoid precursor proteins steps (2)

Answer 19

1) pass through double membrane system if chloroplast at specific contact sites
2) translocate into thylakoid membrane via system similar to SRP and SecYEG

Question 20

peroxisomes function

Answer 20

site for fatty acid oxidation

Question 21

peroxisomes method of translocation

Answer 21

post-translational translocation

Question 22

peroxisomes structure

Answer 22

single membrane organelle

Question 23

peroxisomes import signal

Answer 23

short sequence at C-terminus

- S K L

Question 24

peroxins

Answer 24

proteins that participate in import process into the peroxisome (very poorly understood_

Question 25

Zellweger syndrome

Answer 25

inherited disease caused by defect in importing proteins into peroxisomes (brain abnormality and death after birth)

Question 26

primary hyperoxaluria

Answer 26

inherited disease which peroxisome signal sequence of alanine:glyoxylate aminotransferase is altered
- protein mislocalized to mitochondria and can perform normal function

Question 27

nuclear envelope

Answer 27

double-membrane structure that encloses DNA and defines border of the nucleus
- has pores

Question 28

nuclear envelope exported products

Answer 28

1) tRNA’s

2) mRNA’s

Question 29

nuclear envelope imported products

Answer 29

1) histones
2) DNA/RNA polymerases
3) gene regulatory proteins
4) RNA-processing proteins

Question 30

NPC

Answer 30

nuclear pore complex

- perforate the nuclear envelope

Question 31

fibrils

Answer 31

NPC proteins that form disordered tangle to restrict permeability

Question 32

FG nucleoporins

Answer 32

called this because fibrils are made of repeating Phenylalanine-glycine residues

Question 33

what is the cut off for proteins that cannot enter the nucleus via passive diffusion

Answer 33

larger than 60 kDa

Question 34

NLS

Answer 34

nuclear localization signal for nuclear import

• short sequence of positively charge K and R
• located anywhere on the protein (not important)

Question 35

can fully folded proteins be transported through an NPC

Answer 35

yes

Question 36

importin

Answer 36

proteins that carry cargo proteins that transport the cargo protein.
- binds to NLS and NPC proteins

Question 37

GTP-Ran

Answer 37

complex that binds onto the importin to release the cargo protein

Question 38

GTP on GTP-Ran function

Answer 38

acts as a timer

- when GTP hydrolyzes (slow hydrolysis), the Ran switches conformation and dissociates from the importin

Question 39

Ran on GTP-Ran stands for…

Answer 39

Ras-related nuclear protein

Question 40

where does Ran-GTP bind to the importin

Answer 40

binds to importin on nuclear side of pore (causes receptors to release cargo)

Question 41

what happens the the Importin with Ran-GTP after the cargo is released

Answer 41

transported back to cytosol

Question 42

how does Ran-GTP dissociate from the importin

Answer 42

GTP is hydrolyzed and converted to Ran-GDP

Question 43

how does export of nuclear proteins work

Answer 43

1) Free export receptors go into nucleus
2) Ran-GTP in nucleus promotes cargo binding to the export receptor
3) interaction with fibrils transports the complex to the cytosol
4) hydrolysis of Ran-GTP releases the export receptor and the cargo
5) export receptor returns to the nucleus