Answer to Question #108524 in Cell Biology for K

Question

Using genetic engineering techniques, you have created a set of proteins that contain two
(and only two) conflicting signal sequences that specify different compartments. Predict which
signal would Wln out for the following combinations. Explain your answers.

A. Signals for import into the nucleus and extracellular matrix.

B. Signals for export from the nucleus and import into the peroxisome.

C. Signals for import into mitochondria and retention in the Golgi complex.

Answer 1

a) The protein would enter the ER. The signal for a protein to enter the

ER is recognized immediately, as the polypeptide chain emerges from

the ribosome, whereas nuclear import signals function only after a

protein is fully synthesized and fully folded.

b) The protein would enter the mitochondria. For a nuclear export signal

to work, the protein would have to end up in the nucleus first and

thus would need a nuclear import signal for the nuclear export signal

to be used.

c) The protein would enter the mitochondria. There is no signal for ER

import, so the ER retention signal would not function.