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* Microbodies C-terminal targeting signal *
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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 trifunctional fatty acid beta oxidation pathway enzyme.
 - Mammalian, insect, plants, and Aspergillus uricase.
 - Mammalian sterol carrier protein-2 high molecular form (SCP-X).
 - Mammalian long chain alpha-hydroxy acid oxidase.
 - Mammalian soluble epoxide hydrolase (sEH).
 - Firefly luciferase.
 - Plants glycolate oxidase.
 - Plants glyoxisomal isocitrate lyase.
 - Plants 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) carnitine o-acetyltransferase.
 - 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 beta oxidation pathway.
 - Yeast (C. tropicalis) isocitrate lyase.

-Consensus pattern: [SAGCN]-[RKH]-[LIVMAF]>
-Last update: June 1994 / Pattern and text revised.

[ 1] De Hoop M.J., Ab G.
     Biochem. J. 286:657-669(1992).
[ 2] Gould S.J., Keller G.-A., Subramani S.
     J. Cell Biol. 107:897-905(1988).
[ 3] Gould S.J., Keller G.-A., Hosken N., Wilkinson J., Subramani S.
     J. Cell Biol. 108:1657-1664(1989).
[ 4] Gould S.J., Keller G.-A., Schneider M., Howell S.H., Garrard L.J.,
     Goodman J.M., Distel B, Tabak H., Subramani S.
     EMBO J. 9:85-90(1990).