Which of the following statements regarding secretory protein translocation is NOT true? Hydropathy profiles are used to computa
tionally identify secreted proteins. Type II membrane proteins have a signal sequence targeting them to the ER as well as a signal anchor sequence. Type I membrane proteins contain two signal sequences; one targets the protein to the ER and one is a stop transfer anchor sequence. Type IV membrane proteins contain a mixture of both stop transfer anchor sequences and signal anchor sequences, the order of which determines the protein's orientation in the membrane.
Incorrect statement is: Type II membrane proteins have a signal sequence targeting them to the ER as well as a signal anchor sequence.
Signal peptide or signal sequence is a sequence of amino acids that gets recognized by signal recognition particle (SRP). This sequence is involved in cotranslational translocation into ER, where the protein should be folded. A stop-transfer sequence signals that translation of the protein should continue in the cytosol (not in ER). A signal anchor sequence signals the insertion of protein into the ER membrane.
