Sodium-dependent, pyrimidine- and purine-selective. Involved in the homeostasis of endogenous nucleosides. Exhibits the transport characteristics of the nucleoside transport system cib or N3 subtype (N3/cib) (with marked transport of both thymidine and inosine). Employs a 2:1 sodium/nucleoside ratio. Also able to transport gemcitabine, 3'-azido-3'-deoxythymidine (AZT), ribavirin and 3-deazauridine.