FAD2 and FAD3 can form dimers in yeast cells. Shown are Western blots of extracts of yeast expressing FLAG-tagged constructs of Fad2, Fad3, or Fad2 and Fad3 probed with anti-FLAG antibodies with (+) or without (−) chemical cross-linking (as described under “Experimental Procedures”). Yeast lysates were from cells expressing Fad2 (left panel), Fad3 (middle panel), or Fad2/Fad3 (right panel). The numbers correspond to the molecular masses of protein standards; molecular masses of monomer and dimer are indicated by M and D, respectively. Each panel is representative of at least three independent experiments.