This family includes Hydrogen expression/formation protein HypE Swiss:P24193, AIR synthases Swiss:P08178 EC:6.3.3.1, FGAM synthase Swiss:P35852 EC:6.3.5.3 and selenide, water dikinase Swiss:P16456 EC:2.7.9.3. The function of the C-terminal domain of AIR synthase is unclear, but the cleft formed between N and C domains is postulated as a sulphate binding site [1].

1: X-ray crystal structure of aminoimidazole ribonucleotide synthetase (PurM), from the Escherichia coli purine biosynthetic pathway at 2.5 A resolution. Li C, Kappock TJ, Stubbe J, Weaver TM, Ealick SE; Structure Fold Des 1999;7:1155-1166. PMID:10508786