Nucleobase_cation_symporter-2
Nucleobase cation symporter-2
Family of transport proteins
The Nucleobase cation symporter-2 (NCS2) family, also called the Nucleobase ascorbate transporter (NAT) family,[1] consists of over 1000 sequenced proteins derived from gram-negative and gram-positive bacteria, archaea, fungi, plants and animals. The NCS2/NAT family is a member of the APC Superfamily of secondary carriers.[2] Of the five known families of transporters that act on nucleobases, NCS2/NAT is the only one that is most widespread.[3] Many functionally characterized members are specific for nucleobases including both purines and pyrimidines, but others are purine-specific. However, two closely related rat/human members of the family, SVCT1 and SVCT2, localized to different tissues of the body, co-transport L-ascorbate (vitamin C) and Na+ with a high degree of specificity and high affinity for the vitamin.[4] Clustering of NCS2/NAT family members on the phylogenetic tree is complex, with bacterial proteins and eukaryotic proteins each falling into at least three distinct clusters. The plant and animal proteins cluster loosely together, but the fungal proteins branch from one of the three bacterial clusters forming a tighter grouping.[5] E. coli possesses four distantly related paralogous members of the NCS2 family.[6]