Sorting Proteins

Question 0

Signal Sequence (Start Transfer Sequence)

Answer 0

This is a specific signal on the polypeptide Chain that causes the Ribosome to move toward the ER

Question 1

Endoplasmic Reticulum

Answer 1

-More than 50% of total membrane of cell
-More than 10% of total volume of cell
*Production of
>Transmembrane (intrinsic) proteins
>Secretion Proteins
*Cytosol (+), Lumen (-)

Question 2

Signal Recognition Protein (SRP)

Answer 2

> RNA Molecule that detects the signal sequence

>When SRP binds to Signal Peptide this causes a Pause in Translation

Question 3

SRP Receptor Proteins

Answer 3

• Attached the the roughy ER
• Detects the SRP molecules
• Binds the Ribosome to the ER

Question 4

Protein Translocator

Answer 4

• Allows the protein to enter the ER Lumen
• When binds to the polypeptide chain (activates) the SRP and SRP receptor Fall Off and Translation continues as Translocation begins

Question 5

Extrinsic Membrane Protein Formation

Answer 5

Extrinsic:
>Start transfer sequence is found on the end of the polypeptide
>When the signal peptidase cuts - the Start transfer sequence remains in the membrane (eventually falls off) and the protein is released into the ER Lumen

Question 6

Intrinsic Membrane Protein Formation

Answer 6

Single Pass Transmembrane Proteins
#1-Same as Extrinsic protein formation with the presents of a Stop Transfer Sequence in the middle of the protein
#2-The Start Transfer Sequence is found in the middle and there is no Signal Peptidase present

Double Pass Transmembrane Proteins
-Both Start and Stop Transfer Sequences are found in the middle of the polypeptide chain and no Signal Peptidase is present

Question 7

Protein Coats

Answer 7

-Helps determine what contents to take
-Helps determine where it docks (fuzes)
-Helps “pinch” off vesicles (requires energy)
Ex:
-Clathrin: from Golgi or PM
-CopI: from Golgi
-CopII: from ER

Question 8

Clathrin

Answer 8

• From the Golgi or PM
• Self-assembles into Triskelion Structure (cages)
• Uses Adaptin to attach to the Cargo Receptors

Question 9

1. ) Adaptin
2. ) Cargo Receptors
3. ) Dynamin

Answer 9

Adaptin
>Binds Clathrin to membrane
>Traps transmembrane proteins (including cargo receptors)
Cargo Receptors
>Assure that the right proteins attach to the right cargo molecules
Dynamin
>Uses GTPase to pinch off the vesicles