Question

A protein contains an ER signal sequence at amino acid positions 7 to 15. At amino acids 25 to 40 the protein also contains a mitochondrial signal sequence. First, describe in one sentence each, what the sequence would look like (i.e. amino acid makeup) for ER and mitochondrial localization. Then, answer where does this protein traffic to (can be one word)? Why? Can it traffic to the other organelle at a later time (can be one word)? Why or why not?

Answer 1

Step-by-step explanation:

1. ER signal sequence: The sequence ([n]MLSLRQSIRFFKPATRTLCSSRYLL) is located at the N-terminus and begins with one or more charged amino acids followed by a stretch of 6 to 12 hydrophobic residues. Mitochondrial signal sequence: The sequence ([n]MVAMAMASLQSSMSSLSLSSNSFLGQPLSPITLSPFLQG) is 3 to 70 amino acid long alternating hydrophobic and positively charged amino acids.
2. ER and mitochondria. The ER and mitochondria are known to interact; so the peptide may be translocated from the ER to the mitochondria. The ER retention signal (KDEL), if present it targets the protein to the ER lumen.
3. Yes. It can be trafficked to the mitochondria if it does not have the ER retention signal.