Intracellular Compartments and Protein Sorting 2 Flashcards
What are most mitochondrial proteins encoded in?
nuclear DNA, although some made in mitochondria
Mitochondrial proteins are ______ on ribosomes and _______ into mitochondria
synthesized
imported
Proteins need to ______ outer and/or inner mitochondrial membranes through _________
cross, translocation
What directs proteins to correct compartment in mitochondria?
signal sequences
Where are mitochondrial signal sequences located?
N terminal and internal
_______ charged residues cluster on one end and ________ _______ on other end to form an ________ alpha helix
positively; uncharged hydrophobic; amphiphilic
For mitochondrial signal sequences what doe receptor proteins recognize instead of the precise sequence?
the configuration
On mitochondrial signal sequences, multi subunit protein complexes called ______ mediate translocation
protein translocators
Describe translocase of the outer membrane (TOM)
present in outer membrane
required for import of all nuclear encoded proteins
inserts them in outer membrane
Where is translocase of the inner membrane (TIM) located?
inner membrane
What are the two TIM complexes?
TIM22 TIM23
What does TIM 23 do?
transports soluble proteins into matrix and helps insert membrane proteins in inner matrix
What does TIM 22 do?
mediates the insertion of specific subclass of proteins
What are the two components of TOM and TIM complexes?
receptors for mitochondrial precursor proteins
translocation channels
What does Sorting and Assembly Machinery (SAM) complexes do?
translocate and inserts/folds beta barrel proteins in the outer membrane
What does the OXA complex do?
mediates insertion of proteins synthesized in mitochondria
Precursor proteins entering mitochondria are folder or unfolded?
unfolded
How is the unfolding of precursor proteins maintained?
through interactions with chaperone proteins (cytosolic Hsp 70 family)
import receptors of ______ complex bind signal sequence of incoming proteins
TOM
chaperone proteins are ____ and unfolded protein is fed–signal sequence first into _____ channel
stripped off; translocation
TOM transport protein across the outer membrane to where?
inner membrane space
When a protein binds to TIM complex it moves through channel to where?
matrix
What are signal sequences cleaved off by?
peptidase
Transport through TIM depends on ______
membrane potential
