In biochemical

protein targeting :''This article deals with protein targeting in eukaryotes unless specified otherwise.'' Protein targeting or protein sorting is the biological mechanism by which proteins are transported to their appropriate destinations within or outside the ce ...

, a peroxisomal targeting signal (PTS) is a region of the

peroxisomal A peroxisome () is a membrane-bound organelle, a type of microbody, found in the cytoplasm of virtually all eukaryotic cells. Peroxisomes are oxidative organelles. Frequently, molecular oxygen serves as a co-substrate, from which hydrogen per ...

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

that

receptor Receptor may refer to: * Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a ...

s recognize and bind to. It is responsible for specifying that proteins containing this motif are localised to the peroxisome.

Overview

All peroxisomal proteins are synthesized in the

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The ...

and must be directed to the peroxisome. The first step in this process is the binding of the

to a receptor. The receptor then directs the complex to the peroxisome. Receptors recognize and bind to a region of the peroxisomal protein called a peroxisomal targeting signal, or PTS. Peroxisomes consist of a matrix surrounded by a specific

membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. B ...

. Most peroxisomal matrix proteins contain a short sequence, usually three

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

s at the extreme

carboxy In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic ...

tail of the protein, that serves as the PTS. The prototypic sequence (many variations exist) is

serine Serine (symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − form un ...

lysine Lysine (symbol Lys or K) is an α-amino acid that is a precursor to many proteins. It contains an α-amino group (which is in the protonated form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −C ...

leucine Leucine (symbol Leu or L) is an essential amino acid that is used in the biosynthesis of proteins. Leucine is an α-amino acid, meaning it contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α- ca ...

(-SKL in the one letter amino acid code). This motif, and its variations, is known as the PTS1, and the receptor is termed the PTS1 receptor. It was found that the PTS1 receptor is encoded by the

PEX5 Peroxisomal targeting signal 1 receptor (PTS1R) is a protein that in humans is encoded by the ''PEX5'' gene. PTS1R is a peroxisomal targeting sequence involved in the specific transport of molecules for oxidation inside the peroxisome. SKL binds ...

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

imports folded proteins into the peroxisome, shuttling between the peroxisome and cytosol.

interacts with a large number of other proteins, including Pex8p, 10p, 12p, 13p, 14p. A few peroxisomal matrix proteins have a different, and less conserved sequence, at their amino termini. This PTS2 signal is recognized by the PTS2 receptor, encoded by the PEX7 gene. "PEX" refers to a group of genes that were identified as being important for peroxisomal synthesis. The numerical attributions, such as PEX5, generally refer to the order in which they were first discovered. A distinct motif is used for proteins destined for the peroxisomal membrane called the "mPTS" motif, which is more poorly defined and may consist of discontinuous subdomains. One of these usually is a cluster of basic amino acids (arginines and lysines) within a loop of protein (i.e., between membrane spans) that will face the matrix. The mPTS receptor is the product of

PEX19 Peroxisomal biogenesis factor 19 is a protein that in humans is encoded by the ''PEX19'' gene. Interactions PEX19 has been shown to Protein-protein interaction, interact with: * ABCD1, * ABCD2, * ABCD3, * PEX10, * PEX11B, * PEX12, * PEX ...

References

External links

Protein targeting Signal transduction Short linear motifs {{biochem-stub