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

The subcellular location of two integral membrane-bound fatty acid desatura ses (Fads), Fad2 and Fad3, was elucidated by immunofluorescence microscopic analyses of tobacco suspension cells transiently transformed with differen t epitope-tagged versions of the enzymes. Both myc- or hemagglutinin-tagged Fad2 and Fad3 localized to the same region of the endoplasmic reticulum (E R), as evidenced by their co-localization with the ER lumenal protein calre ticulin, Results from differential permeabilization experiments revealed th at the N-termini of both epitope-tagged Fad2 and Fad3 were exposed on the c ytosolic side of ER membranes, These data define the subcellular location a nd topological orientation of plant desaturases in ER membranes. (C) 2001 P ublished by Elsevier Science B.V. on behalf of the Federation of European B iochemical Societies.