A conserved cysteine is essential for Pex4p-dependent ubiquitination of the peroxisomal import receptor Pex5p - PubMed (original) (raw)

. 2007 Aug 3;282(31):22534-43.

doi: 10.1074/jbc.M702038200. Epub 2007 Jun 5.

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A conserved cysteine is essential for Pex4p-dependent ubiquitination of the peroxisomal import receptor Pex5p

Chris Williams et al. J Biol Chem. 2007.

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Abstract

The peroxisomal protein import receptor Pex5p is modified by ubiquitin, both in an Ubc4p-dependent and -independent manner. Here we show that the two types of ubiquitination target different residues in the NH(2)-terminal region of Pex5p and we identify Pex4p (Ubc10p) as the ubiquitin-conjugating enzyme required for Ubc4p-independent ubiquitination. Whereas Ubc4p-dependent ubiquitination occurs on two lysine residues, Pex4p-dependent ubiquitination neither requires lysine residues nor the NH(2)-terminal alpha-NH(2) group. Instead, a conserved cysteine residue appears to be essential for both the Pex4p-dependent ubiquitination and the overall function of Pex5p. In addition, we show that this form of ubiquitinated Pex5p is susceptible to the reducing agent beta-mercaptoethanol, a compound that is unable to break ubiquitin-NH(2) group linkages. Together, our results strongly suggest that Pex4p-dependent ubiquitination of Pex5p occurs on a cysteine residue.

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