PEX21/YGR239C Summary Help

Standard Name PEX21 1
Systematic Name YGR239C
Feature Type ORF, Verified
Description Peroxin required for peroxisomal matrix protein targeting; acts on proteins containing the PTS2 targeting sequence; interacts with Pex7p; partially redundant with Pex18p; relative distribution to cytoplasmic foci increases upon DNA replication stress; PEX21 has a paralog, PEX18, that arose from the whole genome duplication (1, 2, 3, 4 and see Summary Paragraph)
Name Description PEroXin 1
Chromosomal Location
ChrVII:970053 to 969187 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Gene Ontology Annotations All PEX21 GO evidence and references
  View Computational GO annotations for PEX21
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 5 genes
Large-scale survey
32 total interaction(s) for 16 unique genes/features.
Physical Interactions
  • Affinity Capture-RNA: 1
  • Co-crystal Structure: 1
  • Reconstituted Complex: 6
  • Two-hybrid: 12

Genetic Interactions
  • Dosage Lethality: 1
  • Negative Genetic: 8
  • Synthetic Growth Defect: 2
  • Synthetic Lethality: 1

Expression Summary
Length (a.a.) 288
Molecular Weight (Da) 33,049
Isoelectric Point (pI) 6.67
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrVII:970053 to 969187 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..867 970053..969187 2011-02-03 1996-07-31
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000003471

The biogenesis of peroxisomes requires a group of protein factors referred to as peroxins which are encoded by the PEX genes. Peroxisomal proteins are synthesized on free polyribosomes and imported posttranslationally. The transport of peroxisomal matrix proteins from the cytoplasm to the peroxisome is mediated by two peroxisome-targeting signal sequences (PTS1 and PTS2). Peroxisomal membrane proteins (PMPs) are imported independently of the matrix proteins by a distinct mechanism mediated by the membrane PTS signal (mPTS) (5, 6, 7, 8 and references therein).

Pex7p, Pex18p, and Pex21p are involved in peroxisome biogenesis and the import of peroxisomal matrix proteins that contain the peroxisomal targeting sequence PTS2 (7, 9). The PTS2 is located within the first 20 amino acids and has the consensus sequence H/R-L-X5-H-L (10, 11). Pex7p binds PTS2-containing proteins in the cytoplasm and delivers them to the peroxisomal membrane where Pex18p and Pex21p contribute to their interaction with the peroxisomal import machinery (1, 2, 12).

Two subcomplexes of the peroxisomal import machinery have been defined: the docking subcomplex comprises Pex14p, Pex17p, and Pex13p, while the translocation subcomplex contains Pex2p, Pex10p, and Pex12p. The proteins of the translocation complex expose their RING finger domains to the outer face of the peroxisomal membrane, and act downstream of Pex14p, Pex17p, and Pex13p during the peroxisomal protein import process (13). Association of both subcomplexes into a larger import complex requires Pex8p, an intraperoxisomal protein. Pex8p organizes the formation of the larger import complex from the trans side of the peroxisomal membrane and thus might enable functional communication between both sides of the membrane (13).

Pex18p and Pex21p are partially redundant; import of proteins containing PTS2 is compromised only in the double mutant (1). Both Pex18p and Pex21p are constitutively degraded under normal conditions (14). Pex18p and Pex21p are not widely conserved but Pex20p in Y. lipolytica and N. crassa and Pex5L in mammals have been identified as functional homologs (15, 16).

In addition to its role in the import of peroxisomal matrix proteins, Pex21p has also been proposed to be involved in increasing the affinity of seryl-tRNA synthetase with its tRNA(Ser) substrate (17).

Last updated: 2007-06-28 Contact SGD

References cited on this page View Complete Literature Guide for PEX21
1) Purdue PE, et al.  (1998) Pex18p and Pex21p, a novel pair of related peroxins essential for peroxisomal targeting by the PTS2 pathway. J Cell Biol 143(7):1859-69
2) Stein K, et al.  (2002) Interactions of Pex7p and Pex18p/Pex21p with the peroxisomal docking machinery: implications for the first steps in PTS2 protein import. Mol Cell Biol 22(17):6056-69
3) Byrne KP and Wolfe KH  (2005) The Yeast Gene Order Browser: combining curated homology and syntenic context reveals gene fate in polyploid species. Genome Res 15(10):1456-61
4) Tkach JM, et al.  (2012) Dissecting DNA damage response pathways by analysing protein localization and abundance changes during DNA replication stress. Nat Cell Biol 14(9):966-76
5) Hettema EH, et al.  (2000) Saccharomyces cerevisiae pex3p and pex19p are required for proper localization and stability of peroxisomal membrane proteins. EMBO J 19(2):223-33
6) Sacksteder KA and Gould SJ  (2000) The genetics of peroxisome biogenesis. Annu Rev Genet 34:623-652
7) Purdue PE and Lazarow PB  (2001) Peroxisome biogenesis. Annu Rev Cell Dev Biol 17:701-52
8) Fujiki Y, et al.  (2006) Import of peroxisomal membrane proteins: The interplay of Pex3p- and Pex19p-mediated interactions. Biochim Biophys Acta 1763(12):1639-46
9) Brown LA and Baker A  (2003) Peroxisome biogenesis and the role of protein import. J Cell Mol Med 7(4):388-400
10) Glover JR, et al.  (1994) Mutagenesis of the amino targeting signal of Saccharomyces cerevisiae 3-ketoacyl-CoA thiolase reveals conserved amino acids required for import into peroxisomes in vivo. J Biol Chem 269(10):7558-63
11) Zhang JW and Lazarow PB  (1996) Peb1p (Pas7p) is an intraperoxisomal receptor for the NH2-terminal, type 2, peroxisomal targeting sequence of thiolase: Peb1p itself is targeted to peroxisomes by an NH2-terminal peptide. J Cell Biol 132(3):325-34
12) Heiland I and Erdmann R  (2005) Biogenesis of peroxisomes. Topogenesis of the peroxisomal membrane and matrix proteins. FEBS J 272(10):2362-72
13) Agne B, et al.  (2003) Pex8p: an intraperoxisomal organizer of the peroxisomal import machinery. Mol Cell 11(3):635-46
14) Purdue PE and Lazarow PB  (2001) Pex18p is constitutively degraded during peroxisome biogenesis. J Biol Chem 276(50):47684-9
15) Kiel JA, et al.  (2006) PEX Genes in Fungal Genomes: Common, Rare or Redundant. Traffic 7(10):1291-303
16) Einwachter H, et al.  (2001) Yarrowia lipolytica Pex20p, Saccharomyces cerevisiae Pex18p/Pex21p and mammalian Pex5pL fulfil a common function in the early steps of the peroxisomal PTS2 import pathway. EMBO Rep 2(11):1035-9
17) Godinic V, et al.  (2007) Peroxin Pex21p interacts with the C-terminal noncatalytic domain of yeast seryl-tRNA synthetase and forms a specific ternary complex with tRNA(Ser). FEBS J 274(11):2788-99