Immunocytological localization of two plant fatty acid desaturases in the endoplasmic reticulum

The subcellular location of two integral membrane-bound fatty acid desaturases (Fads), Fad2 and Fad3, was elucidated by immunofluorescence microscopic analyses of tobacco suspension cells transiently transformed with different epitope-tagged versions of the enzymes. Both myc- or hemagglutinin-tagged Fad2 and Fad3 localized to the same region of the endoplasmic reticulum (ER), as evidenced by their co-localization with the ER lumenal protein calreticulin, Results from differential permeabilization experiments revealed that the N-termini of both epitope-tagged Fad2 and Fad3 were exposed on the cytosolic side of ER membranes, These data define the subcellular location and topological orientation of plant desaturases in ER membranes. (C) 2001 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.