Question

Which statement most accurately describes what happens to proteins that lack an ER signal sequence?

They are inserted into the ER membrane but do not enter the ER lumen.
They are inserted into the plasma membrane.
They bypass the ER but enter the Golgi apparatus.
They are released into the cytosol.

Answer 1

The correct answer is: They are released into the cytosol.

A a sequence consisting of 5-30 hydrophobic amino acids on the N-terminus, which is called signal peptide or signal sequence is responsible for directing the transport of the synthesized protein. Proteins that contain such sequence are destined for secretion form the cell (vesicular), for the plasma membrane, the lumen or membrane of either the (ER), Golgi or endosomes. So, when the protein lack the sequence, it is released in the cytosol.