A signal peptide is a short (15-60 amino acids long) peptide chain that directs the post translational transport of a protein. Some signal peptides are cleaved from the protein by signal peptidase after the proteins are transported. Signal peptides may also be called targeting signals or signal sequences. The amino acid sequences of signal peptides direct proteins which are synthesized in the cytosol to certain organelles such as the nucleus, mitochondrial matrix, endoplasmic reticulum, chloroplast, and peroxisome. In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ... Peptides (from the Greek πεπτος, digestable), are the family of molecules formed from the linking, in a defined order, of various amino acids. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... The term signal sequence can refer to any of the following: protein targeting signal peptide This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... The cytosol (as opposed to cytoplasm, which also includes the organelles) is the internal fluid of the cell, and a large part of cell metabolism occurs here. ... In cell biology, an organelle is one of several structures with specialized functions, suspended in the cytoplasm of a eukaryotic cell. ... Plural: nuclei In chemistry and physics, the nucleus (atomic nucleus) is the collection of protons and neutrons in the center of an atom that carries the bulk of the atoms mass and positive charge. ... In biology, the word matrix is used for the material between animal or plant cells, or generally the material (or tissue) in which more specialized structures are embedded, and also specifically for one part of the mitochondrion. ... The endoplasmic reticulum or ER (endoplasmic means within the cytoplasm, reticulum means little net) is an organelle found in all eukaryotic cells. ... Chloroplasts are organelles found in plant cells and eukaryotic algae which conduct photosynthesis. ... Peroxisomes are ubiquitous organelles in eukaryotes. ...

A nuclear localization signal (NLS) is a signal peptide directing to the nucleus and is often a unit consisting of plus-charged amino acids. The NLS normally is located inside the peptide chain. Almost all proteins that are transported to the endoplasmic reticulum have a sequence consisting of 5-10 hydrophobic amino acids on the N-terminus. Most of these proteins are transported from the endoplasmic reticulum to the Golgi apparatus. If these proteins have a particular 4-amino-acids sequence on the C-terminus, these proteins stay in the endoplasmic reticulam. The signal peptide that directs to the mitochondrial matrix has another sequence consisting of an alternate pattern which a few hydrophobic amino acids and a few plus-charged amino acids form. There are two types of signal peptides directing to peroxisome, which are called peroxisomal targeting signals (PTS). One is PTS1, which is made of three amino acids on the C-terminus. The other is PTS2, which is made of a 26-36-amino-acid sequence on the N-terminus. In cell biology, the Golgi apparatus, Golgi body, Golgi complex, or dictyosome is an organelle found in nearly all eukaryotic cells. ...

Types

Following is a list of types of signal peptides:

• N-terminus signal peptides often target the mitochondrial matrix, endoplasmic reticulum and peroxisome.
• C-terminus signal peptides often target the peroxisome.

In biology, the word matrix is used for the material between animal or plant cells, or generally the material (or tissue) in which more specialized structures are embedded, and also specifically for one part of the mitochondrion. ... The endoplasmic reticulum or ER (endoplasmic means within the cytoplasm, reticulum means little net) is an organelle found in all eukaryotic cells. ... Peroxisomes are ubiquitous organelles in eukaryotes. ... Peroxisomes are ubiquitous organelles in eukaryotes. ...

Typical signal peptides

 Transport to the nucleus (NLS) -Pro-Pro-Lys-Lys-Lys-Arg-Lys-Val- 

 Transport to the endoplasmic reticulum H2N-Met-Met-Ser-Phe-Val-Ser-Leu- Leu-Leu-Val-Gly-Ile-Leu-Phe- Trp-Ala-Thr-Glu-Ala-Glu-Gln- Leu-Thr-Lys-Cys-Glu-Val-Phe- Gln- 

 Retention to the endoplasmic reticulum -Lys-Asp-Gln-Leu-COOH 

 Transport to the mitochondrial matrix H2N-Met-Leu-Ser-Leu-Arg-Gln-Ser- Ile-Arg-Phe-Phe-Lys-Pro-Ala- Thr-Arg-Thr-Leu-Cys-Ser-Ser- Arg-Tyr-Leu-Leu- 

 Transport to the peroxisome (PTS1) -Ser-Lys-Leu-COOH 

 Transport to the peroxisome (PTS2) H2N-----Arg-Leu-X5-His-Leu- 

H₂N is the N-terminus of a protein. COOH is the C-Terminus of a protein. Plural: nuclei In chemistry and physics, the nucleus (atomic nucleus) is the collection of protons and neutrons in the center of an atom that carries the bulk of the atoms mass and positive charge. ... The endoplasmic reticulum or ER (endoplasmic means within the cytoplasm, reticulum means little net) is an organelle found in all eukaryotic cells. ... The endoplasmic reticulum or ER (endoplasmic means within the cytoplasm, reticulum means little net) is an organelle found in all eukaryotic cells. ... In biology, the word matrix is used for the material between animal or plant cells, or generally the material (or tissue) in which more specialized structures are embedded, and also specifically for one part of the mitochondrion. ... Peroxisomes are ubiquitous organelles in eukaryotes. ... Peroxisomes are ubiquitous organelles in eukaryotes. ...