BNR_4 is a family which carries the unique sequence motif SxDxGxTW which is so characteristic of the repeats of the BNR family, Pfam:PF02012. It is unclear whether or not this unit is repeated throughout the sequences of this family, but if it is then the family is likely to be bacterial neuraminidase.

1: Conserved sequences in bacterial and viral sialidases. Roggentin P, Rothe B, Kaper JB, Galen J, Lawrisuk L, Vimr ER, Schauer R; Glycoconj J 1989;6:349-353. PMID:2562507