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