Intracellular Compartments and Protein Sorting 1 Flashcards
Dr. Zaidi
Describe the plasma membrane
outer boundary of cells, bilayer
protective barrier
has transporters
signaling
Describe the nucleus
contains the genome
principal site for DNA and RNA synthesis
Describe the cytoplasm
consists of cytosol and cytoplasmic organelles
intermediary metabolism
Describe the endoplasmic reticulum
with ribosomes attached (rough ER), no ribosomes (smooth ER)
protein synthesis, lipid synthesis, protein folding, quality control, storage of calcium, signaling
Describe the golgi apparatus
stacks of disc like compartments
post translational changes on protein and lipids, trafficking
Describe the mitochondria
outer and inner membrane and matrix
energy metabolism, signaling, cell differentiation and cell death
Describe the lysosomes
contain digestive enzymes that degrade organelles and biomolecules
Describe the peroxisomes
small vesicular compartments that contain enzymes used in oxidation reactions
What are the 3 topological categories the cell is divided into?
nucleus and cytosol
organelles in secretory and endocytic pathways
mitochondria
Membrane _________ and ________ allows the lumen of these compartments to _______ with each other and with the ________
budding; fusion; communicate; cell exterior
What is gated transport?
Between nucleus and cytosol through nuclear pore complexes ( active transport and free diffusion)
What is transmembrane transport?
membrane protein translocators directly transport specific proteins from cytosol across an organelle membrane
What is vesicular transport?
membrane enclosed transport intermediates move proteins between various compartment via vesicles
What guides protein transfer/transport to various compartments?
sorting signals
What is a sorting signal?
stretch of amino acids, typically 15-60 residues long
Where is a sorting signal localized?
on N or C terminus or within protein sequence
Multiple scattered sequences in protein may form ______
signal patch
What removes the signal after protein reaches final destination?
signal peptidase
Signal sequence are both necessary and sufficient for what?
protein targeting
_____ properties of sequence are more important than actual sequence
physical
What are signal sequences recognized by?
complementary receptors
What does the signal sequence that functions to import into the nucleus contain?
lysines and arginines
What does the signal sequence that functions to import into mitochondria contain?
positively charged and hydrophobic amino acids
What does the signal sequence that functions to import into ER contain?
hydrophobic amino acids
What does the signal sequence that functions to return to the ER contain?
KDEL
Describe nuclear transport
gated
bidirectional
selective
Proteins needed in the nucleus are imported from where?
cytoplasm
What are nuclear pore complexes composed of?
30 different proteins or nucleoporins
How are nuclear pore complexes arranged?
in octagonal symmetry with one or more aqueous pores
Do nuclear pore complexes transport molecules in one or both directions?
both
In nuclear pore complexes, Transport facilitated by binding of particles to ______ extending from NPC
fibrils
What are nuclear localization signals?
sorting signals that direct molecules to nucleus
What are nuclear localization signals rich in?
positively charged amino acids, lysine and arginine
Where are nuclear localization signals located?
different sites on protein
form loops or patches on surface
Nuclear localization signals are recognized by ______
nuclear import receptors
Nuclear import receptors are _____________ proteins that bind to _______ on protein and to ______ proteins present on fibril that extend into cytoplasm
soluble cytosolic; nuclear localization signal, nuclear pore complex
What kinda of repeats do NPC proteins have? What do they serve as?
have phenylalanine glycine (FG) repeates
serve as binding sites for import receptors
Nuclear export relies on a ________ on molecules that need to go out of nucleus.
nuclear export signals
Nuclear export signals need complementary what?
nuclear export receptors
Proteins that contain NLS and NES shuttle back and forth between what?
nucleus and cytosol
Steady state localization depends upon _________ of transport
relative rate
If rate of import is greater than export, it is considered ______
nuclear
Changing rate of import/export can do what?
change location of protein
