Two new kinase folds. a) Riboflavin kinase (PDB|1q9s ). Loops L1 and L2 are shown in magenta. Residues 1 (Pro33) and 2 (Phe97) interact with the adenine ring of the nucleotide. Residues 3 (Thr34) and 4 (Asn36) coordinate the Mg2+ cation. Residues 4 (Asn36) and 5 (Tyr98) interact with the phosphate tail of the nucleotide. In this and all other structure figures, the ATP analog is colored orange, substrate molecules are purple, and Mg2+ cations are green balls. Ribbon diagrams were made using the MOLSCRIPT  program. b) Dihydroxyacetone kinase nucleotide-binding domain (PDB|1un9 ). Residues 1 (Leu435), 2 (Thr476), and 3 (Met477) pack around the adenine ring of the nucleotide. Residues 4 (Ser431) and 5 (Ser432) interact with the phosphate tail of the nucleotide. Residues 6 (Asp380), 7 (Asp385), and 8 (Asp387) are involved in coordinating the two Mg2+ cations. Dashed lines indicate disordered regions in the structure.