All are true regarding diphtheria toxin except ?

Option 4 Corynebacteriam diphtheriae does not need to be toxigenic to establish localized infection. Option 1, 2, 3 Mechanism of Action of diphtheria toxin Has 2 fragments: Fragment A (active unit) Fragment A is internalized into the host cells and then causes- ADP ribosylation of elongation factor 2(EF2) - inhibition of EF2- irreversible inhibition of translation step of protein synthesis- cell death. Fragment B (binding unit) Binds to the host cell receptors (such as epidermal growth factor) Helps in entry of fragment A. Toxin Production is dependent on: Phage coded: DT is coded by b corynophage carrying tox gene. Iron concentration: Toxin production depends on optimum iron concentration (0.1 mg/liter). DT repressor gene (DtxR) is an iron dependent negative regulator of DT production and iron uptake in C.diphtheriae.