Exam 3: Ch 13 Targeting of Proteins to Mitochondria, Chloroplasts, Peroxisome Flashcards Preview

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Flashcards in Exam 3: Ch 13 Targeting of Proteins to Mitochondria, Chloroplasts, Peroxisome Deck (40):
1

structure of mitochondria and chloroplasts

2 phospholipid bilayers

outer membrane, inner mebrane, intermembrane space, internal matrix (lumen)

2

structure of peroxisome

single membrane and single luminal matrix

3

proteins encoded by mitochondrial or chloroplast DNA are...

synthesized on ribosomes within the organelles and directed to the correct subcompartment immediately

4

the majority of proteins in mitochondria and chloroplasts are encoded by genes in the...

nucleus, and imported into the organelles after synthesis in cytosol by free ribosomes

5

do proteins targeted to the mitochondria, chloroplast, and peroxisome have a signal sequence?

yes, part of the mature protein

cleaved in mitochondria and chloroplast

not cleaved in peroxisome

6

in mitochondria and chloroplasts, protein import requires ____ and occurs where

energy

occurs at points where the outer and inner membranes are close together

may need 2 targeting sequences and 2 translocon systems

7

import to matrix requires

a matrix-targeting sequence

goes to outer mitochondrial memb. import receptor --> import pore (outer memb)

simultaneous transport occurs through TIM through the inner membrane into the matrix

8

are chaperonins found in the matrix?

yes, help final folding of matrix proteins

9

studies with ______ proteins show important features of mitochondrial import

chimeric

a precursor must be unfolded to enter import pores

10

_ energy inputs are needed to import proteins into mitochondria

3

ATP hydrolysis by chaperone proteins

molecular motor of chaperone + TIM

proton-motive force (H+ electrochemical gradient)

11

targeting of proteins to areas other than the matrix of the mitochondria require..

more than 1 signal sequence

12

targeting to inner membrane

3 pathways

1: same as targeting to matrix + stop-transfer sequence

2: insertion into inner membrane

3: incorporates multiple segments into inner membrane

13

targeting to intermembrane space

2 pathways

1: matrix targeting sequence + sequence that blocks translocation of protein across inner membrane

2: direct transport to intermembrane space without a matrix targeting sequence

14

targeting to outer-membrane

beta barrel structure

interact with general import pore

transfer to SAM

15

targeting of chloroplast _____ proteins is similar to import of mitochondrial matrix proteins

stromal

ex. enzymes of calvin cycle (rubisco)

16

stromal import sequence

similar to matrix import sequence

transport entirely ATP hydrolysis dependent

involves a receptor and import pore

17

thylakoid

series of interconnected membranous sacs

proteins in thylakoids carry out photosynthesis

18

many proteins in thylakoids are synthesized in the...

cytosol as precursors with multiple targeting sequences

stromal import sequence, thylakoid lumen sequence

19

_ pathways for transporting proteins from the stroma to the thylakoid have been identified

4

closely related to translocation across bacterial membrane

20

4 pathays of thylakoid transport

1: involves an SRP with a translocon

2: ATP hydrolysis

3: related to Oxa1 protein

4: metal-containing cofactors, H+ electrochemical gradient

21

as peroxisomes are enlarged by addition of protein and lipid, they eventually...

divide to form new ones

22

peroxisomes use what types of enzymes

ones that use molecular oxygen to oxidize substates

generates hydrogen peroxide

abundant in liver cells

23

what sequence targets proteins to the peroxisome (matrix)

SKL at the c terminus

peroxisomal targeting sequence 1 (PTS1)

24

peroxisomal protein import mechanism

protein with PTS1 binds to soluble carrier protein in cytosol

carried and binds to receptor in peroxisome matrix

protein imported

carrier protein recycled

25

is a different set of proteins required to embed proteins into the peroxisomal membrane?

yes

26

nuclear envelope

two membranes that separate the nucleus from the cytoplasm

continuous with ER membrane

27

nuclear pores

span both membranes of nuclear envelope

allow transport of proteins and other molecules into and out of the nucleus

made of nuclear pore complex made from nucleoporins

28

imported nuclear proteins have what sequence

nuclear localization sequence

29

do proteins enter the nucleus in a folded state?

yes

30

environment of the nuclear pore

aqueous pore

31

3 types of nuclearporins

structural: form scaffold

membrane: highly curved region

FG: line channel of NPC

32

what receptor is needed for nuclear transport

a nuclear transport receptor

33

two required cytosolic components for nuclear transport

Ran

nuclear transport receptor

34

Ran

small monomeric G protein (GTP/GDP)

35

nuclear transport receptor

binds the NLS on a cargo protein and to FG nucleoporins

in nucleoplasm, interacts with Ran-GTP which goes back to the cytoplasm

then Ran turns GTP --> GDP and releases the nuclear transport receptor back into cytoplasm

36

what is exported from the nucleus to cytoplasm

proteins

tRNA

ribosomal subunits

37

nuclear export requires what signal

a nuclear export signal (NES)

38

what receptor is needed for nuclear export

exportin 1

interacts with Ran-GTP and NES

39

most mRNAs are exported from the nucleus by a ___-independent mechanism

Ran-independnt

40

mRNA export from nucleus

mRNA associated with an hnRNP forming an mRNP

uses mRNP exporter that interacts with FG nucleoporins

uses ATP hydrolysis

driven by a concentration gradient