Protein Sorting and Trafficking

Question 0

how are proteins destined for mitochondria transported?

Answer 0

By chaperone proteins in the unfolded state as only one a,ino acid fits through translocation channel.

Question 1

In the ER what constitutes the signal sequence and how does it differ to that for the mitochondria, nucleus and lysosome?

Answer 1

9 hydrophobic amino acids.
3 Arg residues.
Basic +ve amino acids.
Mannose-6-phosphate tag.

Question 2

what modifications are made to proteins in the ER and in the Golgi? What happens to incorrectly folded proteins?

Answer 2

disulphide bonds may form.
Sugars are added (increases ss diversity).
they don’t enter the Golgi

Question 3

what are glycosyltransferases?

Answer 3

Golgi enzymes which add sugars to proteins on red blood cells giving blood groups.

Question 4

what is a stop transfer sequence?

Answer 4

v. hydrophobic sequence of ~ 20-22 amino acids = length of a membrane - remain as TRANSMEMBRANE SEGMENTS.

Question 5

where can the mannose 6 phosphate receptor be found and what does it do?

Answer 5

in the golgi

directs proteins into transport vesicles destined for lysosomes.