D-gluconate(out) + H(+)(out) => D-gluconate(in) + H(+)(in)
d-gluconate(out) + h(+)(out) => d-gluconate(in) + h(+)(in)
D-gluconate(out) + H(+)(out) => D-gluconate(in) + H(+)(in)
d-gluconate(out) + h(+)(out) => d-gluconate(in) + h(+)(in)