Figure 2.—

Viability of esa1 catalytic-site mutants. (A) LEU2-marked plasmids bearing ESA1, esa1-E338Q, or esa1-C304S were transformed into a BY4743-derived esa1∷kan strain carrying an ESA1 URA3 plasmid. Resulting strains were then streaked onto 5-FOA to counterselect the ESA1 URA3 plasmid. (B) An esa1-E338Q allele was knocked into the genomic ESA1 locus in a W303 diploid strain, which was then sporulated and dissected. The esa1-E338Q allele supports viability (right, small colonies), while an esa1∷kan allele does not (left) unless covered with an ESA1 plasmid (middle).