09a: Protein Trafficking Flashcards
T/F: synthesis of all proteins begins on cytoplasmic ribosomes.
True
Proteins translated on cytoplasmic ribosomes are targeted to:
- Cytoplasm
- Mitochondria
- Nucleus
Proteins translated on RER ribosomes are targeted to:
- Cell membrane
- Lysosomes
- Cell secretion
What’s the power house of protein synthesis?
RER
Information that determines site of a protein’s localization is found in its (primary/secondary/tertiary) structure.
Primary
Cytoplasmic protein have which signal?
No signal
Mitochondrial protein have which signal?
Pre-sequence with amiphipathic character (hydrophobic and positively-charged AA) on N-terminus
Nuclear proteins have which signal?
Lys-Lys-Lys-Arg-Lys
Membrane proteins have which signal?
Core of hydrophobic AA near N terminus
Secretory proteins have which signal?
Core of hydrophobic AA near N terminus
Lysosomal proteins have which signal?
Mannose-6-P
SRP stands for (X) and is similar in composition to (Y).
X = Signal Recognition Particle Y = snRNPs (has RNA and protein components)
What’s the function of SRPs?
Bind signal peptide on secretory, membrane, lysosomal proteins that have begun translation on cytoplasmic ribosomes
Once SRP binds (X), translation is paused until:
X = signal peptide
SRP binds its receptor on ER membrane
T/F: Ribosomes on ER are fixed on the membrane.
False - when SRP binds signal peptide, it carries ribosome to ER to continue translation of the protein
T/F: Signal peptide is removed from mature polypeptide chain once translation and translocation is complete.
True - cleaved by signal peptidase
Simple, one-pass transmembrane proteins have (X) sequence that’s composed of (Y) AA.
X = stop-transfer Y = core of hydrophobic
Glycosylation of Asn residues occurs in (ER/Golgi/cytoplasm).
ER
Glycosylation of Ser residues occurs in (ER/Golgi/cytoplasm).
Golgi
Glycosylation of Thr residues occurs in (ER/Golgi/cytoplasm).
Golgi
The initial glycans added to (X) in ER have which key component?
X = Asn (X-Ser/Thr)
Mannose
In ER, which regions/bonds are too difficult to assemble with chaperones alone?
- Pro regions
- Disulfide bonds
(Require additional enzymes)
Cutting/modifying sugars on (X) residues, that were added in the ER, is done in which organelle?
X = Asn
Golgi
When lysosomal hydrolase precursor enters golgi, (glucose/mannose) is attached.
Mannose - glucose trimmed off
(Cis/trans) golgi is closer to RER.
Cis
Lysosome precursor undergoes which change in cis golgi?
Addition of phosphorylated sugar to mannose
Lysosome precursor undergoes which change in trans golgi?
Removal of sugar from phosphorylated sugar complex that was added to mannose in cis-golgi (uncovering signal)
Lysosomal storage diseases are usually results of:
deficient or dysfunctional enzymes (thus, buildup of toxic metabolites)
How/when do mitochondrial proteins transport into the organelle?
Post-translationally; signal peptide binds receptor on outer mito membrane and complex forms to translocate protein to matrix
T/F: There are no molecules that can simply diffuse across the nuclear membrane.
False - very small molecules can
(X) proteins make up nuclear pores.
X = Nup (nucleoporins)
(X) form the nucleus diffusion barrier as well as the (Y).
X = FG nups Y = nuclear basket
(X) bind nuclear transport receptors, aka (Y), and regulate their entry into nucleus.
X = FG nups Y = importins
T/F: Importins themselves enter the nucleus to drop off cargo (nuclear protein).
True
The nuclear lamina is located on (X) and made up of (Y).
X = inside of nuclear envelope Y = lamin proteins
Nuclear lamina functions:
- stabilize nuclear structure
2. Anchor nuclear pores
