This family represents the C-terminal region of the bifunctional riboflavin biosynthesis protein known as RibC in Bacillus subtilis. The RibC protein from Bacillus subtilis has both flavokinase and flavin adenine dinucleotide synthetase (FAD-synthetase) activities. RibC plays an essential role in the flavin metabolism [1]. This domain is thought to have kinase activity [2].

1: Regulation of riboflavin biosynthesis in Bacillus subtilis is affected by the activity of the flavokinase/flavin adenine dinucleotide synthetase encoded by ribC. Mack M, van Loon AP, Hohmann HP; J Bacteriol 1998;180:950-955. PMID:9473052

2: Crystal structure of flavin binding to FAD synthetase of Thermotoga maritima. Wang W, Kim R, Yokota H, Kim SH; Proteins 2005;58:246-248. PMID:15468322