Transmembrane proteins, Golgi, COP

Question 1

Abnormal protein tracking and mislocution in diseases

Answer 1

• A peroxisome is a type of organelle known as a microbody.
• They are found in virtually all eukaryotic cells and are involved in a small number of enzymatic reactions
• (e.g. catabolism of very long chain fatty acids, reduction of reactive oxygen species, biosynthesis plasmalogens—phospholipids critical for the normal function of mammalian brains and lungs)

Question 2

Zellweger syndrome

Answer 2

• Zellweger syndrome is inherited in an autosomal recessive manner
  ○ Severe brain developmendefects
  ○ Hypomyelination
  ○ Apnea
  ○ Abnormal renal function
  ○ Patient usually does not survive beyond one year

Question 3

Cystic Fibrosis

Answer 3

• Cystic fibrosis (CF) is caused by a mutation in the gene cystic fibrosis transmembrane conductance regulator (CFTR).

-The most common mutation, ΔF508, is a deletion of three nucleotides, resulting in a
loss of the amino acid phenylalanine (F) at the 508th position on the protein.

-This mutation account for two-thirds (66–70%) of CF cases worldwide.

Question 4

Co-translational protein import

Answer 4

-How soluble proteins get into the endomembrane system

Question 5

Co-translational protein import (step 1)

Answer 5

-The signal recognition particle (SRP) binds to a signal -sequence in the amino terminal end of the growing polypeptide and halts translation

Question 6

Co-translational protein import (step 2)

Answer 6

The SRP binds to the receptor on the ER membrane

Question 7

Co-translational protein import (step 3)

Answer 7

The SRP brings the ribosome to a transmembrane channel; the SRP dissociates; protein synthesis resumes and the growing polypeptide chain is threaded through the channel

Question 8

Co-translational protein import (step 4)

Answer 8

The protein ends up in the lumen of the ER where it may remain, be transported to the lumen of another organelle or be secreted our the cell

Question 9

How transmembrane proteins are integrated into a membrane (A)

Answer 9

Proteins with signal - anchor sequences are threaded through a channel int he ER membrane until the signal anchor sequence is encountered

Question 10

How transmembrane proteins are integrated into a membrane (B)

Answer 10

The ER channel releases the proteins into the membranes

Question 11

How transmembrane proteins are integrated into a membrane (C)

Answer 11

When translation is completed the protein remains in the membrane

Question 12

Synthesis of integral membrane proteins

Answer 12

• How transmembrane proteins are integrated into a membrane
• The mechanism is for type 1 single-pass transmembrane proteins
• It is more complex (extra steps) for multi - pass proteins
• N-terminal sequences, which are also called signal sequences, direct proteins to their respective organelles.
• When they arrive at the organelle other intrinsic sequences within the protein directs them to the correct compartment or membrane.