Fig. (5) Relative 14C lysoPtdCho content in 14C acetate labeling experiments conducted following co-expression of either PLB1 or PLB2 or PLB3 with PLA2, respectively, in the plb123 triple mutant. All strains are designated by those plasmids expressed in the plb strain as explained for Table 3 and indicated in Table 1. Starting from a cell density of 0.1 (OD600) in 20 ml of glucose medium, cells of plbPLA2EV, plbPLA2PLB1, plbPLA2PLB2 and plbPLA2PLB2 were labeled with 30 ┬ÁCi 14C-sodium acetate for 10 hours, then induced in galactose medium for 5 hours. The total lipids were extracted and resolved by two dimensional thin layer chromatography and the 14C lysoPtdCho was quantified (see Materials and methods). The plb123 triple mutant expressing only the PLA2, designated as plbPLA2EV, accumulated 14C lysoPtdCho to 1.0 % of the total phospholipid (PL) fraction, as was typical in previous experiments (See Fig. 3). The plbPLA2PLB1, plbPLA2PLB2 and plbPLA2PLB3 co-transformants exhibited 60-75% reductions in the relative 14C lysoPtdCho content. Values are the average of 2 replicates.