Types of Signals

• - secretory proteins
• - N-terminus
• - destines it to the ER
• - polypeptide moves through cotranslationally

• -proteins that normally reside in the ER
• -at the C-terminus
• -tells receptors that they belong in the ER and helps them return them back to here
• -capturing and returning them back into COPI-coated vesicles

• -for ER membrane proteins
• -involves two closely-linked basic residues, most commonly KKXX
• - n/a
• - n/a

• -lysosomal enzymes
• -on lysosomal enzymes
• -recognized by M6P receptors, which enable capturing and concentration into clathrin-coated vesicles
• -n/a

• -peroxisome-destined proteins
• -PTS receptors bind to them

• -chloroplast destined cells
• -transit peptide
• - guarantees that the polypeptide will enter the stroma and then is cleaved by a processing peptidase

• -polypeptides destined to go to a thylakoid membrane or lumen
• -transit peptide

- n terminus

mRNA binds to ribosomeà ribosome begins translating that sequence of bases into amino acid sequences--> signal peptide is synthesized on N-terminusà signal recognition particle binds to it and the ribosomeà translation stopsà SRP guides the complex to a SRP receptorà two sorts of interactions: SRP to SRP receptor and ribosome to transloconà SRP is releasedà translation continues as the polypeptide is being translated through the pore