Nucleoside permease that transports adenosine and guanosine. Does not show any transport activities towards cytidine, adenine, guanine, uridine, and uracil. Mammalian nucleoside transport inhibitors dipyridamole and NBMPR inhibit adenosine transport by NUP. Predicted to be a substrate for cleavage by KEX2. Belongs to the NUP family.