2.A.57.2.3
High affinity, concentrative nucleoside (inosine, formycin, guanosine):H⁺ symporter, NT2 (Stein et al., 2003). Mutations confer drug (formycin) resistance and drug transport deficiency (Galazka et al. 2006). Asp₃₈₉ is critical for transporter function without affecting ligand affinity or plasma membrane targeting, but Asn₁₇₅ and Asp₃₈₉ (when mutated as a second site mutation) lie in close proximity to each other; second-site suppressor mutations cluster to one region of the transporter, suggested that Asp₁₇₅ is conformationally sensitive (Arastu-Kapur et al. 2005). Development of glutamatergic/cholinergic postmitotic human neurons is induced by short-term treatment with nucleoside analogues such as cytosine β-D-arabinofuranoside,  2'-O-methyl substituted 2-deoxy-β-D-ribofuranosyl residues as glyconic moieties, and cladribine (Raasch et al. 2015; González-Burguera et al. 2016).