intracellular compartments and protein sorting 1 Flashcards
What is the plasma membrane ?
outer boundary of cells, bilayer
- protective barrier, has transporters, and signaling
what is the nucleus?
Contains the genome
priniciple site for DNA and RNA synthesis.
What is the cytoplasm?
consists of cystol and cytoplasmic organelles
intermediary metabolism (glycolosis occurs here too)
What is the endoplasmic recticulumn?
- Rough ER (ribosomes)
- Protein synthesis
- Smooth ER ( no ribosomes)
- lipid synthesis
- Protein folding, quality control, storage of calcium, signaling.
What is the golgi apparatus ?
Stacks of disc-like compartments
-post translational changes on proteins and lipids, trafficking (like glycolslation)
What is the mitochondria?
Outer and inner membrane and matrix
Energy metabolism, signaling, cell differentation and cell death
What is a lysosomes?
Contains digestive enzymes that degrade organelles and biomolecules
What is a perioxisome
small vesicular compartments that contain ezymes used in oxidation reactions
What are the three topological componets and what characteristic do they have in common?
- Nucleus and cytosol (communcate through Nuclear pore complex)
- Organelles in secretory and endocytic pathways (ER, golgi appartatus, endosomes, and lysomes) (communicate with each other through vesicles)
- mitochondria
They all heavily communicate withing there own compartments
How does the secretory and endocytic pathway communicate?
membrane budding fusion allows the lumen of these compartments to communicate with each other and the cell exterior
What is gated transport and what does it occur between?
Active transport and free diffusion
b/w the nucleus and cytosol through nuclear pore complexes
What is transmembrane transport?
membrane protein translocators directly transport specfic proteins from cytosol across an organelle
cytosole to mitochondria, ER, Plastids, Peroxisomes
UNIDIRECTIONAL
What is vesicular transport?
Membrane enclosed transport intermediates move proteins b/w various compartments via vesicles
occurs b.w
- golgi and late endosome
- golgi and early endosome
- Golgi and Cell exterior
- Golgi and secretory vesciles
- late endosome and lysosome
- Late endosome and early endosome
- Early endosome and cell exterior
- secretory vesciles and cell exterior
What are sorting signals?
guide protein transfer / transport proteins to various compartments
- AA sequence around 15 -60
- Localized in N & C terminus or w/in the protein seq.
Are necessary and suffiecent for protein targeting
signals recongized by complementary receptors
What are signal patches and when does they communicate
Multiple catter sequences in the protein that are sorting signals
once 3D folding is completed they are more related to each other
What are signal peptidases?
May remove signal after protein reaches final destination
What are the four different types of signal sequences?
- import into nucleus
- postivily charged
- lysine (K) /Argine (R) rich sequence thats in no particular order
- import into mitochondria
- Combination of postive and hydrophobic induces coil shap that facilitates binding to mitochondria
- import into er
- hydrophobic AA is signal
- return to ER
- KDEL (lysine - Aspartic acid - glutamic acid - leucine )
What are the characteristics of nuclear transport?
Gated, bidriectional, selective
- proteins needed in nucleus imported from cytosol
- (histones, DNA, Rna poly topoismerase, gene regulation proteins )
- tRNA and mRNA synthesized in the nucleus are exported out to sytosol
What are nuclear pore compexes (NPC)
- 30 different proteins or nucleoporins
- octagonal symmetry w/ 1 or more aquaporins
- transport bidirectionally
- Transport faciliated by binding of particles to fibril
- passive diffusion of small molecules and faciliated transport
- Size of macromolecules that enter nucleus by active transport
CONTAIN FG (PHENYLALANINE GLYCINE ) REPEATS which are BINDING SITES FOR NIRS on FIBRILS
Cargo is released in nucleus and NIR returns to cytoplasm
What are Nuclear localization signals ?
- NLS direct molecules to nucleus
- short sequecnes rich in lysine and argenine (remember import to nucleus )
- selective import of proteins to nucleus
- many different sites on proteins in fhte form of loops and patches
What are NIR (nuclear Import Receptors) ?
- recongizes NLS (specfic)
- Soluble cytsolic proteins
- Bind to NLS on protein
- NPC proteins present on fibrils
Recpetrors can binds dissociate, and rebind to adjacent FG repeats
cargo is released in the nucleus and NIRS return to Cytosol
What are is an adapter protein and how does it work?
- It is a nuclear import receptor.
- Has two types of binding
- direct binding and indirect binding via adapter protein
- Recongizes NLS
- Occurs in Cytosol
What is nuclear export?
Works in oppostie direction but in similar pattern
relies on NES on exported molecules but must a have complementary NER
Bind to NPC and cargo presnt in Nucleus
binding, dissociation, and rebinding,
cargo released in cytoplasm.
how does ran GTP and ran GDP work
Concept: Gradient of RAN confirmaton drives nuclear transport
Simple
Import receptor and cargo enter nucleus via FG sites on fribrils of NPC proteins
RAN GTP binds to compex of import receptor and cargo
Binding causes release of cargo
RAN-GTP and import receptor leave nucleus
In Cytoplasm RAN GTP is hydrolzed to Ran GDP
Receptor is released from RAN GDP in cytoplasm and is reader for another cycle
What are shuttling proteins ?
Proteins that contain both NLS and NES
Shuttle b/w cytosol and Nucleus
Steady state localization depends on relative rate of transport
If import > Export then transport is nuclear
How does transport and gene regulatory proten relate?
Transport stringently controlled
kept out of nucleous until needed
transport controlled by NLS and NES being turned on or off
Mechanism include phosphorylation, proteolysis, binding to inhibitory proteins
What does SREBP and SCAP do?
RELATED TO CHOLESTEROL regulation
SREBP - is a sterol response element binding proteiin. Once its cleaved by protease will leave ER and enter nucleaus to promote creation of STEROID
SCAP - SREBP cleavage activation protein ( Cholesterol binds to and inhbits recruitment of proteases for cleavage)
