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