(A) Riboflavin and (B) iron–sulfur clusters.
†RibB function in Helicobacter pylori is catalyzed by the bifunctional enzyme RibBA.
NifS/IscS: Cysteine desulfurase; NifU/IscU: (Iron–sulfur) cluster scaffold protein; RibA: GTP cyclohydrolase II; RibB: 3,4-dihydroxy-2-butanone 4-phosphate synthase; RibC: Riboflavin synthetase; RibD: Pyrimidine deaminase; RibE: 6,7-dimethyl-8-ribityllumazine synthase.