nucleoside:proton symporter activity xanthosine:proton symporter activity xanthosine permease activity Enables the transfer of a solute or solutes from one side of a membrane to the other according to the reaction: xanthosine(out) + H+(out) = xanthosine(in) + H+(in). GO:0015537 molecular_function xanthosine:hydrogen ion symporter activity xanthosine transmembrane transporter activity