Submitted on August 1, 2003
Revised on October 1, 2003
Accepted on October 13, 2003
Distinct roles of endoplasmic reticulum cytochrome b5 and fused cytochrome b5-like domain for rat ù6-desaturase activity
Hervé Guillou, Sabine ;D'Andrea, Vincent Rioux, Romain Barnouin, Stéphanie Dalaine, Frédérique Pédrono, Sophie Jan, and Philippe Legrand
Biochemistry Dept., ENSAR-INRA, Rennes 35042
Corresponding Author: Philippe.Legrand{at}agrorennes.educagri.fr
The Delta6-desaturase catalyses key-steps in long-chain polyunsaturated fatty acid biosynthesis. While the gene coding for this enzyme has been isolated in diverse animal species, the protein structure remains poorly characterised. In this work, rat Delta6-desaturase expressed in COS-7 cells was shown to localise in the endoplasmic reticulum. As the enzyme contains a N-terminal cytochrome b5-like domain, we investigated through site-directed mutagenesis the role of this domain for the enzyme activity. The typical HPGG motif of the cytochrome b5-like domain and particularly histidine in this motif is required for the activity of the enzyme, whatever the substrate. Neither endogenous COS-7 cytochrome b5 nor co-expressed rat reticulum cytochrome b5 could rescue the activity of mutated forms of Delta6-desaturase. Moreover, when rat reticulum cytochrome b5 was co-expressed with wild-type desaturase, both protein interacts and Delta6-desaturase activity was significantly increased. The identified interaction between both proteins is not dependent on the desaturase HPGG motif. These data suggest distinct and essential roles of both the desaturase cytochrome b5-like domain and free reticulum cytochrome b5 for Delta6-desaturase activity.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
