Met123, Met206, and Met230 are important for HypT activity. Viability assay of C600 hypT− cells carrying (A) an empty plasmid pBAD22 (control) or expressing wild-type hypT, and the hypT mutants (B) M123Q, M206Q, M230Q, M280Q, and M284Q, (C) M123I, M206I, M230I, M280I, and M284I, and (D) C4S, C25S, C150S, C178S, and C242 after treatment with 3.5 mM HOCl for 90 min. Results are expressed as mean ± SD (n ≥ 3).