EXAM 2 ZAIDI Flashcards
What are the 3 categories for topological compartmentalization?
- NUCLEOUS -> CYTOSOL (via nuclear pore complex)
- ER, GOLGI APP, ENDOSOMES, AND LYSOSOMES TO EACH OTHER (via vecicles)
- MITOCHONDRIA (transmembrane transport)
What ways does protein trafficking take place?
- Gated transport
- nucleus and cytosol via nuclear pore complexes
- active transport and free diffusion
- Trans membrane Transport
- Protein translocators
- Cytosol to Organelle membrane (direct and more specfic proteins)
- Vesicular transport
- vesicles
- (ER,Golgi,Endosome,Lysome, Cell Exterior, Secretory vescles)
How do Protein Sorting Signals guide protein transport?
- N or C terminus or Within protein sequence (15 - 60 residues long) may form signal patch
- Necessary and sufficient for protein targeting
- recongized by complementary receptors
- may be removed via signal peptidases at final destination
What is Nuclear transport and its characterisitics?
- Bidirectional, Selective, and Gated
- use Nuclear localization sequences
- Which are rich in LYSINE (L) (LYS) and ARGINE (R) (ARG)
- Proteins needed in nucleus are imported to Cytosplasm
- RNA /DNA poly and Histones , Gene regulatory
- tRNA and mRNA exported to cytosol
What are nuclear pore complexes? “NPCs”
- Nuclear Envelope
- composed via nucleoporins
- octagonal symmetry
- transports is BIDIRECTIONAL
- passive diffusive of small molecules and facilitated transport
- Binding of particles to fibrils extending from NPC
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What are Nuclear Localization Signals?
NLS are sorting signals direct molecules toward nucleus
Postivley Charged seq. rich in LYSINE and ARGININE
On different sites on protein form loops or patches
selective import
What is Nuclear Import?
- NLS is recongized by Nuclear Import Receptors (NIRS)
- Soluable and bind to NLS and to NPC protein (fibrils that extend to cytoplasm)
- NPC binding via phenylalanine and glycine (F G) repears
- Binding sites for receptors
- move via cyclic binding,dissociating, rebinding to adjacent FG repeats
- Cargo released inside nucleus and NIR returned to Cytoplasm
What is Nuclear Export?
- Moves cargo from nucleus to Cytoplasm
- vis Nuclear export signals (NES) and Nuclear export receptors (NER)
- NER BIND to cargo present in nucleus and NPC proteins
- BInding,Dissociating, and rebinding across NPC
- Cargo released in Cytoplasm
know this
SREBP - sterol response element binding protein
proteases cleaves SREBP which releases a release factor that enters NPC and triggers cholesterol formationr
SCAP - SREBP cleavage activation protein
responds to cholesterol and recruits proteases when there is a low concentration
What are characterisitcs mitochondrial proteins
mostly encoded in nuclear DNA
synthesized on ribosomes and imported to mito.
Proteins cross ouuter and/or inner mito. membrane (TRANSLOCATION)
directed via signal sequences
What are the characterisitics of mitochondiral signal sequences ?
N term. and internal signal sequences
POSTIVELY CHARGED residues cluster on one end and UNCHARDED HYDROPHOBIC on the other end tof orm amphophillic helix
Receptor proteins focus on Configuration of structures rather than precise sequence
mediated by protein translocators
What are your protein translocators ?
- TOM
- 2 components receptro for mito. precursoe proteins + translocation channels
- outer membrane protein ; import all nuclear endoded proteins
- SAM “Sorting and Assembling Machine”
- translocates and inserts/folds beta barrel proteins in outer membrane
- TIM 22
- Inner membrane; mediates the insertion of specfic subclass proteins (ATP, ADP, Pi transport)
- TIM 23
- Soluable proteins into matrix and helps and inserts into inner membrane
- OXA
- Mediates insertion of all proteins synthesized in the mitochondria. Also some proteins already present in the matrix brought from the outside
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- Mediates insertion of all proteins synthesized in the mitochondria. Also some proteins already present in the matrix brought from the outside
How does the protein import into the protein mitochondrial martix
What Parts of import into the mitochondiral matrix require energy?
just know this
What is the difference between Cotranslational and Post-translational Tranlocational?
Co translational translocation - transcription is haulted using SRP and ribosome binds to ER membrane and resumes trancription
Postranslation occurs after translation
What is the ER single sequence?
vary in AA
have 8 or non polar amino acids
ER singla sequence is guided by
- Signal recongition particle SRP
- SRP receptor
How is the protein directed Ribosomes to ER membrane for cotranslational tranport ?
What is the structure of the ER translocator
Translocator present in the ER membrane
Water filled pore
core is made of sec 61 complex
pore gated by short helix which opens and closes pore when needed
What is the structure of the SRP molecule?
made of different poly peptides plus a small RNA molecule
large hydrophobic pockey lined with methonies
cyles b.w the ER membrane and cytosl and binds to the ER signal sequence
Pocket can accommodate hydrophobic signal sequences of different size, shape, and sequence
What is vesicular transport?
transpot of cargo via transport vesicles that bud of from primary compartment and fuse witht he next one?
different shapes and sizes: small spherical and large irregular or tublar
DIRECTIONAL!!!!!
What are the three types vesicular transport ?
Biosynthetic secretory - > COPII
Endocytic pathway -> Clathrin
Retrieval Pathway -> COPI
What are clathrin coated vesicles?
3 large and 3 small polypeptide chains; three legged structured = triskelion
triskelions assemble into a basket like structure
binds to adapter proteins to form a second layer between the cage and the membrane
trap various transmembrane proteines including receptors that capture soluble cargo inside vesicles
MEDIATE TRANSPORT FROM THE GOLGI APPARATUS AND THE PLASMA MEMBRANE
How is clathrin dissasembled and reassembled?
curvature is indued -> coated buds -> adaptor proteions bidn to clathrin and cargo receptors -> selective recrutiment of cargo molecules -> clathrin coat is lost after vesicle formation
What pinches the clathrin bud to form vesicle?
Dynamin
What is involved in the first step in Clathrin bud formation?
