Protein Synthesis in Nervous System Flashcards
What 3 main proteins do AA sequence for?
Cytosolic proteins
Nuclear/mitochondrial proteins
Membrane proteins
What are cytosolic proteins folded by?
Chaperones
What is N-acylation?
Transfer of an acyl group to the N terminus
Allows for better interaction with membrane proteins eg. G proteins
What is isoprenylation?
Thioacylation of a C-terminal cysteine
Helps proteins cycle between membrane and cytosol
What is phosphorylation?
Phosphorylation of hydroxyl group of Ser, Thr or Tyr residues
Can change enzymatic or interactive properties
What is ubiquitination?
Addition of ubiquitin to lysine residues in an aa sequence
What 3 enzymes are required for tagging?
Ubiquitination activating (E1)
Conjugating (E2)
Ligase (E3)
What does ubiquitin tagging a protein do?
Tags a protein for processing/degradation by the proteasome
Important for synaptogenesis and long term memory
What do nuclear proteins contain?
Nuclear localization signal (NLS)
What does the NLS do?
Target nuclear protein entry into the nucleus in an energy-dependent reaction
Which proteins need active import to pass through nuclear pores?
proteins < 10nm
When do mitochondrial proteins reach native conformation?
After import into target organelle
What is the mitochondrial signal sequence?
20-80 aa basic helix with hydrophilic (+) residues on one side and hydrophobic (-) residues on the other
What happens if the membrane protein doesn’t contain hydrophobic sequences?
Co-translational transfer continues until C terminus is transferred across membrane
Becomes free protein in lumen
What happens if the membrane protein does contain hydrophobic sequences?
Undergo co-translational transfer until ‘stop transfer’ sequence is reached
Forms integral membrane proteins
What are disulfide linkages?
(Cys-S-S-Cys)
Define teritary structure
Doesn’t occur in cytosol
What is N-linked glycosylation?
Addition of a polysaccharide chain to amino groups of asparagine residues
Diversifies conformation and function of proteins
How are proteins transported through the golgi apparatus?
Via transport vesicles
What are the two protein coats?
COP1 and COP11
how do ER vesicles enter the trans-golgi network (TGN)?
Arrive at cis side of the golgi
fuse with membranes of golgi cisternae
deliver contents into golgi complex
move to trans side
What modifications do proteins undergo as they reach trans side?
N-linked and O-linked glycosylation
Phosphorylation
Sulfation
What do these trans modifications cause?
Increase hydrophobicity of the protein - makes them more resistant to protein degradation
How do plasma proteins leave TGN?
Constitutive secretion - vesicles continually secreted in a non-regulated manner
How do neurohormones leave TGN?
Regulated secretion - concentrated into large dense-core vesicles and targeted to axons
How do synaptic proteins leave TGN?
unknown
some - transported along neuronal cytoskeleton
others - synthesized and assembled at synapse
What is required for chemotrophic response?
Local protein translation
What is localised mRNA actively trafficked by?
RNA binding proteins (RBPs)
What do RBPs form complexes with?
RNA granules
What do RBPs complexes allow for?
mRNA to be redistributed to the synapse along microtubule molecular motors
