ER

Question 1

Reticulons

Answer 1

Unique ER integral membrane proteins that possess a hair pin secondary structure

Regulate ER membrane curvature (bending)
- Controls whether it forms a round tubule or a flattened cisternae

Question 2

RER

Answer 2

Mostly cisternae with bound ribosomes

Involved in protein and membrane phospholipid synthesis

Question 3

SER

Answer 3

Mostly curved tubules, lacking ribosomes

Involved in Ca storage and hormone synthesis

Question 4

Subdomains

Answer 4

Outer nuclear membrane

PAM (PM Associated membrane)

MAM (Mitochondria associated membrane)

ERES

Question 5

ER targeting signal

Answer 5

8-15 hydrophobic amino acids on N terminus of nascent polypeptide

Question 6

SRP

Answer 6

Signal Receptor Protein

Hetero-dimeric ER integral membrane protein complex

Question 7

Sec61 translocon

Answer 7

Multi protein complex consisting of several ER integral membrane protein subunits (i.e. Sec61 α, β, and ɣ) that form an hour glass shaped aqueous pore

Contains a pore ring of 6 hydrophobic a.a. located at the narrowest diameter of the pore
- Amino acid side chains acts as a gate

Question 8

Signal Peptidase

Answer 8

ER integral protein/protease that cleaves signal sequence as it enters ER lumen

Question 9

Reticuloplasmins

Answer 9

Chaperones that operate in the ER

Bind to nascent soluble or membrane proteins and mediate their proper folding and oligomeric assembly
Prevents protein aggregation