PROSITE documentation PDOC00299

Microbodies are a class of small, single membraned organelles to which belong peroxisomes, glyoxysomes, and glycosomes. Microbody proteins are synthesized on free polysomes and imported into the organelle post-translationally. Unlike the import of proteins into mitochondria, chloroplasts or the ER/secretion pathway, import into microbodies does not generally require the removal of a presequence [1]. It has been experimentally shown [2,3,4] that, in some peroxisomal proteins, the targeting signal (PTS) resides in the last three amino acids of the C-terminus. This consensus sequence is known as 'S-K-L' (Ser-Lys-Leu), although some variations are allowed in all three positions. As the peroxisomal targeting signal also seems to be recognized by other microbodies, it is now [1] known as the C-terminal microbody targeting signal (CMTS).

It must be noted that not all microbody proteins contain a CMTS; some seem to contain an internal CMTS-like sequence, but it is not yet known if it is active as such. Finally, a few proteins are synthesized with an N-terminal presequence which is cleaved off during import.

Microbody proteins known or thought to contain a CMTS are listed below.

Mammalian D-amino acid oxidase.
Mammalian acyl-coenzyme A oxidase (but not the fungal enzymes).
Mammalian and yeast (S. cerevisiae) carnitine o-acetyltransferase.
Mammalian trifunctional fatty acid β oxidation pathway enzyme.
Mammalian, insect, plants, and Aspergillus uricase.
Mammalian sterol carrier protein-2 high molecular form (SCP-X).
Mammalian long chain α-hydroxy acid oxidase.
Mammalian soluble epoxide hydrolase (sEH).
Firefly luciferase.
Plants glycolate oxidase.
Plants glyoxisomal isocitrate lyase.
Plants and fungal glyoxisomal malate synthase.
Trypanosoma glycosomal glucose-6-phosphate isomerase.
Trypanosoma glycosomal glyceraldehyde 3-phosphate dehydrogenase.
Yeast (H. polymorpha and Pichia pastoris) alcohol oxidase (AOX).
Yeast (H. polymorpha) dihydroxy-acetone synthase (DHAS).
Yeast (S. cerevisiae) catalase A.
Yeast (S. cerevisiae) citrate synthase.
Yeast (S. cerevisiae) peroxisomal malate dehydrogenase.
Yeast (C. boidinii) peroxisomal protein PMP20.
Yeast (C. tropicalis) hydratase-dehydrogenase-epimerase (HDE) from fatty acid β oxidation pathway.
Yeast (C. tropicalis) isocitrate lyase.
Aspergillus niger monoamine oxidase N.
Candida albicans vacuolar aspartic protease PRA1.

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1	Authors	De Hoop M.J., Ab G.
1	Source	Biochem. J. 286:657-669(1992).

2	Authors	Gould S.J., Keller G.-A., Subramani S.
	Title	Identification of peroxisomal targeting signals located at the carboxy terminus of four peroxisomal proteins.
	Source	J. Cell Biol. 107:897-905(1988).
	PubMed ID	2901422

3	Authors	Gould S.J., Keller G.-A., Hosken N., Wilkinson J., Subramani S.
	Title	A conserved tripeptide sorts proteins to peroxisomes.
	Source	J. Cell Biol. 108:1657-1664(1989).
	PubMed ID	2654139

4	Authors	Gould S.J., Keller G.-A., Schneider M., Howell S.H., Garrard L.J., Goodman J.M., Distel B., Tabak H., Subramani S.
	Title	Peroxisomal protein import is conserved between yeast, plants, insects and mammals.
	Source	EMBO J. 9:85-90(1990).
	PubMed ID	2104803

Microbodies C-terminal targeting signal

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