This family consists of the sodium/proline symporter (proline permease) from a number of Gram-negative and Gram-positive bacteria and from the archaeal genus Methanosarcina. Using the related pantothenate permease as an outgroup, candidate sequences from Bifidobacterium longum and several from archaea are found to be outside the clade defined by known proline permeases. These sequences, scoring between 570 and -40, define the range between trusted and noise cutoff scores. [Transport and binding proteins, Amino acids, peptides and amines]
Jiyao W et al.(2023). "The conserved domain database in 2023.",