Session 3: Protein Targeting, The Secretory Pathway & Endocytosis

Question 1

functin of membrane topology stop signals?

Answer 1

decide if protein is membrane
bound of soluble

Question 2

function of routing signals?

Answer 2

(decide where the protein goes

Question 3

function of sorting signals?

Answer 3

once on route decides further route(s)

Question 4

Function of retention signal?

Answer 4

decides how long protein stays on route

Question 5

function of no signal?

Answer 5

(some protein remain in the cytosol & have no need for a
signal e.g. lactate dehydrogenase; synthesised and functions in
cytosol

Question 6

The protein signal is a …

Answer 6

… genetic code, that gets translated into a polypeptide sequence within the primary structure

Question 7

How to study peptide signals as a researcher?

Answer 7

1) transfection
biochenical approach
genetic approach

Question 8

whats the transfection approach?

Answer 8

• Create retroviral plasmid construct with
  signal genetic code in the ORF
• Clone in protein genetic sequence
  of a protein that normally resides in
  cytosol
• Signal peptide will direct the protein to a desired organelle
• Subcellular fractionation and immuno-blot for the presence of protein in the desired organelle fraction.

Question 9

whats the biochemical approach?

Answer 9

• Radioactive labelled protein
• Specific signal sequence previously
  identified (bioinformatics)
• Protein is transported to specific organelle (in vitro)