choline(in) + n H(+)(out) => choline(out) + n H(+)(in)
choline(in) + n h(+)(out) => choline(out) + n h(+)(in)
choline(in) + n H(+)(out) => choline(out) + n H(+)(in)
choline(in) + n h(+)(out) => choline(out) + n h(+)(in)