Na(+)/proline cotransporter PutP and related proteins; solute binding domain.
Escherichia coli PutP catalyzes the Na+-coupled uptake of proline with a stoichiometry of 1:1. The putP gene is part of the put operon; this operon in addition encodes a proline dehydrogenase, allowing the use of proline as a source of nitrogen and/or carbon. This subfamily also includes the Bacillus subtilis Na+/proline cotransporter (OpuE) which has an osmoprotective instead of catabolic role. Expression of the opuE gene is under osmotic control and different sigma factors contribute to its regulation; it is also a putative CcpA-activated gene. This subfamily belongs to the solute carrier 5 (SLC5) transporter family.
Comment:based on the structures of Vibrio parahaemolyticus vSGLT (SLC5), Aquifex aeolicus LeuT (SLC6), and the NCS1, Microbacterium liquefaciens Mhp1, bound with Na+, functional studies of Escherichia coli PutP (SLC5) and mammalian NIS (SLC5), and mutational analysis of vSGLT
Comment:one of two Na+ binding sites in Aquifex aeolicus LeuT, where it is referred to as the Na binding site 2
Jiyao W et al.(2023). "The conserved domain database in 2023.",