Question

Which of the following is NOT essential for cotranslational translocation of protein into the endoplasmic reticulum?

A.A stop-transfer anchor sequence;

B.A signal recognition particle;

C.An ER signal sequence;

D.Ribosomes;

E.An ER membrane translocon

Answer 1

(A) A stop transfer signal sequence is NOT essential for translocation. It prevents translocation and inserts itself into the membrane.

Rest of them are essential as explained below.

Ribosome provides a motive force to push the peptide into the lumen.

Signal Recognition Particle is cytoplasmic and conserved sequence required in translocation.

ER signal sequence forms a hairpin loop structure which later gets cleaved by a peptidase.

ER membrane translocon forms TRAP-Translocon associated protein complex. It increases translocation efficiency by binding to Sec61.