Effect of amino acid substitution on the ability of PtdMTP1 to protect against Zn2+ toxicity in yeast. The Zn-hypersensitive yeast strain zrc1 Δ, transformed with pYES2 bearing the mutated variants of PtdMTP1 was grown at 30°C in SD with 2% galactose (SD) until O.D. 600 nm = 1. Serial dilutions were spotted on SD or on SD + 15 mM ZnCl2 (15 mM Zn). Photographs were taken after 6 days of growth at 30°C. For each mutation different yeast transformants were used and gave the same results. The amino acid substitutions along with their topological positions are shown on the left. EV: empty vector; PtdMTP1: wild type protein.