C domain of IsdA protects S. aureus against 1 μM bovine Lfcin killing activity. The following strains were used: ⧫, Newman (wild type); ▪, SRC105 (isdA); ▴, SRC108 (isdAΔNEAT); •, SRC109 (isdAΔC); □, SRC105(pSRC001); and ⋄, SRC105(pMK4). The data for strains Newman, SRC108, and SRC105(pSRC001) overlap extensively, as do the data for strains SRC105, SRC109, and SRC105(pMK4). The data are the means of three independent experiments.