enterobactin(out) + H(+)(in) => enterobactin(in) + H(+)(out)
enterobactin(out) + h(+)(in) => enterobactin(in) + h(+)(out)
enterobactin(out) + H(+)(in) => enterobactin(in) + H(+)(out)
enterobactin(out) + h(+)(in) => enterobactin(in) + h(+)(out)