Zaidi Protein Sorting 2 Flashcards
What are the steps of Memory creation?
1 Encoding
2 Storage
3 Consolidation
4 Retrieval
Most mitochondrial ___ are encoded in ___ DNA (although some are made in mitochondria with mitochondrial translation). They are synthesized on ___ and imported into ___.
Proteins, nuclear
Ribosomes, mitochondria
Define:
Translocation
The movement of proteins, crossing the outer and/or inner mitochondrial membranes.
Define: Mitochondrial Signal Sequences
___ residues cluster on one end and ___ on the other end to form an ___.
Specific receptor proteins recognize the ___ as opposed to the ___.
Protein translocators…
Function to direct proteins to correct mitochondrial compartment.
On N terminus or internal in sequence.
Positively charged, uncharged hydrophobic, amphiphilic alpha helix
Alpha helical configuration, precise sequence
Are multi-subunit protein complexes that mediate transport
Translocase of the outer membrane (TOM) is present in ___, required for ___, inserts them into the ___.
Translocase of the inner membrane (TIM) is present in ___.
Two TIM complexes (22 and 23)
22- function?
23- function?
Outer mitochondrial membrane, import of all nuclear encoded proteins, outer membrane
Inner membrane only (according to new research)
- TIM23 transports soluble proteins into matrix and helps insert membrane proteins in INNER membrane
- TIM22 mediates the insertion of a specific subclass of proteins.
2 components of TOM and TIM complexes are…
The SAM complex (sorting and Assembly Machinery)…
The OXA Complex…
- receptors for mitochondrial precursor proteins, translocation channels
- SAM translocates and inserts/folds beta barrel proteins in the outer membrane
- mediates insertion of proteins synthesized in mitochondria
Precursor proteins are ___ when they enter the mitochondria. This process is maintained through interactions with ___.
Import receptors on ___ bind signal sequence of incoming protein. Once bound, the ___ proteins are stripped off.
Unfolded protein is then fed through TOM, signal sequence first, into the translocation channel and across the ___ space.
Then, the protein binds to the ____ and moves through its channel, reaching the mitochondrial ____.
Finally, once in the mito matrix, ____ cleaves off the signal sequence.
Unfolded, chaperone proteins (Hsp 70, helps maintain unfolded state of protein).
TOM complex. chaperone (Hsp70).
Intermembrane space.
TIM Complex. Matrix.
Peptidase.
The dissociation of bound, cytosolic Hsp70 occurs when the protein moves through the TOM complex, this requires energy from ____.
Transport through TIM, located in the inner membrane, is driven by ___ ___.
Once the protein reaches the matrix ____ releases the protein. This is a(n) ___ dependent step.
___ helps fold the imported protein. This is also a(n) ___ dependent step.
ATP Hydrolysis (ATP –> ADP + Pi)
Membrane potential.
Mitochondrial Hsp70. ATP.
Hsp60. ATP.
The ER is organized into a __ of __ __ and __. ER membrane is continuous with the __ __.
The inner space is called the…
ER plays a central role in the synthesis of __ and __
The ER is the site of production for all __ __.
Network, branching tubules, sacs, nuclear membrane.
ER Lumen
Protein, lipids.
Transmembrane proteins.
ER signal sequences vary in __ sequence
The have __ or more __ amino acids at the center
What two components guide the signal sequence to the ER membrane?
SRP is made of __ different ___ bound to a single small ___ molecule.
SRP cycles between ER membrane and cytosol and binds to ER signal sequence.
SRP is __ shaped with ___ ___ ___ lined by ___.
Pocket can accommodate hydrophobic signal sequences of different: __, __, __
Amino Acid
8, non-polar
1- signal recognition particle (SRP),
2-SRP receptor
Rod, large hydrophobic pocket, methionine
Size, shape, sequence
(Translocation across ER)
SRP wraps around the ___ ___ ___
One end binds to the ER signal sequence of emerging protein and the other end to ____.
it _______ transiently giving enough time for ___ to enter ER membrane.
SRP-ribosome complex binds to …
This interaction brings the assembly to a …
SRP and receptor released and protein translocated across the ER membrane into the lumen.
Large ribosomal subunit
Elongation factor binding site
Blocks protein synthesis, protein
SRP Receptor
Translocator
The translator is in the…
Has a ___ pore
Core of the translocator is made of ___
Has __ subunits with largest subunit surrounding the __ pore
Pore is gated by ___ which opens and closes pore as needed
ER membrane
Water filled
Sec61 complex
3, central
Short helix
What are the steps of protein translocation across the ER?
The final step is cleaving of the signal by this protein, ___, which then causes the signal to escape from a lateral opening in the pore.
SRP binds to ER signal sequence in protein and brings it to ER membrane
Signal sequence interacts with a specific site within the pore thereby opening the pore (Called start-transfer signal).
Dual recognition ensures specificity
Also interacts with lipid core of ER membrane
Signal peptidase.
Describe the process of trans membrane protein integration.
What is the stop transfer signal?
Similar to soluble proteins:
N terminal sequence initiates translocation
Some portions of protein will pass through membrane and others will not
A hydrophobic region (stop transfer signal) in the polypeptide stops transfer process before entire polypeptide is translocated
Anchors protein in membrane (after start-transfer signal has been cleaved and released)
Lateral gating helps remove cleaved start-transfer peptide and to integrate stop-transfer signal to bilayer
In multiple TM proteins several combinations of start- and stop- transfer determine the topology of the protein
Protein import into outer membrane:
Protein first passes through ___ complex. It then binds to ___ proteins. Next, it binds to the ___ complex located in the ____ mitochondrial membrane.
What is the function of SAM?
TOM. chaperone. SAM. outer.
SAM inserts and folds proteins into outer membrane.
