Biosynthesis and Cell Membranes Flashcards
Ribosomal proteins make up
50 proteins in large subunit 33 proteins in small subunit
rRNA make up
- 5S, 5.8S, 28S for large subunit
- 18S for small subunit
Decodes the codons in mRNA Bind the amino acid and deliver it to the growing polypeptide chain
tRNA
ribosomes without tag go where?
They stay in the cytoplasm as cytosolic protein
If the protein needs to go anywhere else besides nucleus, peroxisomes, or mitochondria, then it will need to go through to the
ER first and then if going elsewhere beyond the ER, will need further processing in the golgi
as the ribosome rRNA is translating mRNA into the protein, the nascent protein is simultaneously being translocated to the ER
co-translational translocation
What Gets Translocated?
- ER Membrane and Soluble proteins
- Golgi complex
- Lysosomal Proteins
- Plasma membrane proteins
- Vesicular proteins
Players in co-translational translocation
- SRP in cytosol
- SRP receptor in ER membrane = places protein in translocon.
- Translocon (channel) = opening to get into ER. Sec61 = is the translocon channel that receives the nascent protein.
- Cleave Signal sequence = cleave so that it is free to leave the ER membrane
- Elongation continues of the protein
- Folded protein = final product
SRP binds ribosomes to a docking protein in
RER
Intergral membrane protein with amino terminus inside the lumen
Contain an N-terminal signal sequence that targets them to the ER and an internal hydrophobic sequence that is the hydrophobic alpha helix.
First part is just like that of a secretory protein cotranslational translocation
Hydrophobic residues stop transfer of the chain thru the translocon
Hydrophobic residues allow anchoring in phospholipid bilayer and lateral movement
Type I
Intergral membrane protein with carbohydrate terminus in the lumen
- Do NOT have a cleavable N-terminal ER signal sequence
- Posess an internal hydrophobic sequence which serves as both a signal and an anchor sequence
- The carboxy end enters via co-translational translocation
Type II
multipass integral membrane protein
Each transmembrane region determines the topology and the signal and anchor sequences.
Type III
N-linked glycosylation happens in the RER due to what sugar?
Dolichol
to Asparagine
Protein export from the Golgi Stacks
- Protein cargo binds to membrane receptor
- Membrame receptor binds ADAPTIN
- Adaptin assembles a basket of CLATHRIN, which shapes the vesicle & attracts increasing amounts of cargo
- Coated vesicle leaves the Golgi
In vesicular budding the direction of trafficking depends on
coating (COP I or COP II)
coats vesicles transporting proteins from the cis-Golgi back to the rough endoplasmic reticulum (ER) and between Golgi compartments. This type of transport is termed as retrograde (backwards) transport.
COP I
coats vesicles transporting proteins from the rough endoplasmic reticulum to the cis-Golgi. This process is termed anterograde (forwards) transport.
COP II
a coat protein with diverse functions. The most important functions are (1) endocytosis and vesicle trafficking to endosomes, which includes specialized endocytosis of fluids known as pinocytosis, as well as (2) vesicle transport to lysosomes.
Clathrin
Lysosomal Enzymes Are Sorted to the Proper Destination Because They Are Attached to
Mannose-6-phosphate
Has extensive RER
Plasma Cells
Seals the translocon pore sec-61
BiB
added to misfolded proteins (death tag)
Ubiquitin
When misfolded proteins bind to BiP, this allows _______ to dimerize
IRE1
Site of lipid synthesis
SER
SER of liver cells contain enzyme (e.g., G6-P’ase), responsible for
glycogen synthesis
Once inside the rER ______, _________ are cleaved and folded
cisterna, lumenal proteins
Translation
Proteins for rER Membrane Possess a
“stop” sequence
Label the N and C ends of each integral membrane protein
Coated vesicles move between:
rER and Golgi and between Golgi and Cell Membrane
