Figure 3.

Complementation analysis of APR1. (A) E. coli strain A522 was transformed with λYES, APR1, or a plasmid carrying the E. coli TrxA gene, pPMR18 (27). Transformed colonies were selected on Lennox broth medium containing 100 μg/ml Amp. Ten colonies from each transformation were replica plated onto minimal medium containing 30 μg/ml Cys, and on to minimal medium lacking Cys. (B) APR1 or its parent vector λYES was used to transform three different mutant strains of E. coli, cysH-PAPS reductase (JM96), cysC-APS kinase (JM81A), or cysD-ATP sulfurylase (JM240). A representative colony from each transformation was replica plated onto minimal medium containing 30 μg/ml Cys and onto minimal medium lacking Cys. Only the plate with medium lacking Cys is shown. All the strains grew on the medium in which Cys was provided. The plates were incubated at 30°C for 48 hr prior to photography.