This family contains component I of bacterial heptaprenyl diphosphate synthase (EC:2.5.1.30) (approximately 170 residues long). This is one of the two dissociable subunits that form the enzyme, both of which are required for the catalysis of the biosynthesis of the side chain of menaquinone-7 [1].

1: Two subunits of heptaprenyl diphosphate synthase of Bacillus subtilis form a catalytically active complex. Zhang YW, Koyama T, Marecak DM, Prestwich GD, Maki Y, Ogura K; Biochemistry 1998;37:13411-13420. PMID:9748348