1. signal peptide is a short peptide chain that guides the newly synthesized protein to transfer to the secretory pathway, and its length is 5 ~ 30 amino acids. Usually refers to the amino acid sequence of the nitrogen terminal in the newly synthesized peptide chain, which is used to guide the transmembrane transport (localization) of protein.

After the start codon, there is an RNA region encoding hydrophobic amino acid sequence, called signal peptide sequence, which is responsible for guiding protein to subcellular organelles with different membrane structures.

2. Guiding peptide, also called guiding sequence, is the nitrogen terminal signal of protein synthesized on free ribosomes.

3. Transporter peptide is a leader sequence of 12 to 60 amino acid residues, which guides protein synthesized in cytosol into mitochondria and chloroplasts. These peptides are usually rich in basic amino acids, but almost no acidic amino acids. Threonine and serine are usually common. Transporter peptides recognize special membrane proteins, but do not migrate to target cells, but are removed by peptidase. Different transport peptides do not seem to have conserved sequences. Transporter peptides are targeted after translation. Some mitochondria and plastid protein do not have these resectable N- terminal sequences. The pathway in the target seems to be influenced by carboxyl terminal or protein internal sequence. Transport peptides locate some protein on the membrane of organelles.