Ca(2+)(in) + n H(+)(out) <=> Ca(2+)(out) + n H(+)(in)
ca(2+)(in) + n h(+)(out) <=> ca(2+)(out) + n h(+)(in)
Ca(2+)(in) + n H(+)(out) <=> Ca(2+)(out) + n H(+)(in)
ca(2+)(in) + n h(+)(out) <=> ca(2+)(out) + n h(+)(in)