Mitochondria and Chloroplasts - Mitochondria Dynamics

Question 1

what does mitochondrial fusion often occur in response to

Answer 1

cell stress due to increased need for coordinated functioning of mitochondria network

Question 2

what does mitochondrial fusion require

Answer 2

coordinated fusion of both mitochondrial membranes

Question 3

what order to the membranes fuse in

Answer 3

first outer, then inner

Question 4

why is there an order of fusion

Answer 4

it is essential to maintain mitochondrial sub compartmentalization (homeostasis)

Question 5

what are the 2 GTPase mitofusins

Answer 5

Mfn1
Mfn2

Question 6

what are Mfn1 and Mfn2

Answer 6

integral outer membrane proteins that possess cytoplasmic-facing GTPase domain and long coiled coil, protein interaction domain

Question 7

where are Mfn1 and Mfn2 located

Answer 7

adjacent mitochondria

Question 8

what does proper Mfn1/2 binding get regulated by

Answer 8

other mitochondrial outer membrane proteins

Question 9

what does phospholipase D convert

Answer 9

cardiolipin into phosphatidic acid

Question 10

what is phosphatidic acid

Answer 10

cone shaped lipid

Question 11

what is OPA1

Answer 11

integral inner membrane-bound mitofusin that contains inter membrane space-facing GTPase domain

Question 12

what does prohibition ensure

Answer 12

that OPA1-mediated fusion occurs only between different inner membranes

Question 13

what does prohibition prevent

Answer 13

self fusion of cristae within same mitochondrion

Question 14

what do all nuclear encoded mitochondrial proteins possess

Answer 14

unique targeting sequences

Question 15

what do specific sequences of amino acids serve as

Answer 15

zipcodes to mediate protein targeting from cytoplasm to surface of the mitochondrion or to 1 of 4 mitochondrial subcompartments

Question 16

what is mitochondrial protein targeting pathway very dependent on

Answer 16

proteins final location in mitochondrion

Question 17

what do most matrix-destined proteins possess

Answer 17

20-50 amino-acid long matrix targeting sequence

Question 18

where is the matrix targeting sequence located

Answer 18

nascent proteins N-teminus

Question 19

what does the matrix targeting sequence consist of

Answer 19

amphipathic alpha-helix

Question 20

what is the matrix targeting sequence responsible for

Answer 20

targeting nascent matrix protein to cytoplasmic surface of mitochondrion and subsequent translocation across outer and inner membranes

Question 21

what does cytosolic Hsp70 do

Answer 21

maintains conformation of nascent protein in partially unfolded, import-competent state

Question 22

what is the mitochondrial RNA cloud

Answer 22

mRNAs encoding mitochondrial proteins often enriched in cytoplasm surrounding mitochondria

Question 23

what does mRNA localization get mediated by

Answer 23

RNA-binding proteins on mitochondrial outer surface

Question 24

what does mRNA localization result in

Answer 24

translation taking place immediately adjacent to mitochondrial surface

Question 25

what does mRNA localization allow for

Answer 25

site specific control of mitochondrial gene expression

Question 26

what does mRNA localization facilitate

Answer 26

efficient post translational protein targeting to mitochondria

Question 27

what does the import receptor complex consist of

Answer 27

Tom20
Tom22
several accessory proteins

Question 28

what do the accessory proteins in the import receptor complex serve as

Answer 28

scaffold to mediate subsequent precursor protein transfer from complex to general import pore

Question 29

what does the general import pore primarily consist of

Answer 29

Tom40

Question 30

what is Tom40

Answer 30

integral outer membrane protein

Question 31

how do most mitochondrial proteins access mitochondria initially

Answer 31

through Tom4

Question 32

what does the transmembrane channel allow for

Answer 32

protein translocation across (or into) the outer membrane

Question 33

what does the inner membrane channel consist of

Answer 33

Tim17
Tim23
Tim44

Question 34

where are general import pore and inner membrane channel adjacent to each other

Answer 34

contact sites

Question 35

what are contact sites

Answer 35

places where outer and inner membranes are closely appressed

Question 36

how are contact sites maintained

Answer 36

by interactions of Tom40 and Tom23/17

Question 37

where is matrix Hsp70 located

Answer 37

matrix face of inner membrane channel via binding to Tim44

Question 38

what kind of protein is matrix Hsp70

Answer 38

inner membrane channel accessory protein

Question 39

what does matrix Hsp70 act as

Answer 39

molecular motor

Question 40

how does matrix Hsp70 act as a molecular motor

Answer 40

Tim44-bound Hsp70 undergoes ATP dependent conformational changes that pulls protein into matrix and prevents backsliding of protein into cytoplasm

Question 41

what is required for cytosolic Hsp70 to maintain bound precursor protein

Answer 41

ATP hydrolysis

Question 42

what is import partially driven by during protein translocation

Answer 42

H+ electrochemical gradient across inner membrane - established during electron transport

Question 43

how does the H+ electrochemical gradient work

Answer 43

positively charged residues in amphipathic matrix-targeting sequence are attracted to less positively charged matrix

Question 44

what does step 7 of matrix protein targeting and import represent

Answer 44

additional requirement for energy input