In Bacillus subtilis, family member Swiss:P21341 (PAI 2/ORF-2) was found to be essential for growth [1]. The SUPERFAMILY database finds that this domain is related to FMN-binding domains, suggesting this protein is also FMN-binding.

1: A novel Bacillus subtilis gene involved in negative control of sporulation and degradative-enzyme production. Honjo M, Nakayama A, Fukazawa K, Kawamura K, Ando K, Hori M, Furutani Y; J Bacteriol 1990;172:1783-1790. PMID:2108124