The crystalline structure of F 1,6-BPase of thermophillic archaea, Sulfolobus tokodaii was obtained by X-ray diffraction (figures 2 & 3) that show the alpha and beta sheets. F 1,6-BPase is a 385 amino acid long hypothetical protein with formula mass of 40122.6 Daltons. It has a residue conservation of 359 identified residues on chain A. The structure of F 1,6-BPase is made up of 3 beta sheets, 6 beta hairpins, 7 beta bulges, 15 strands, 14 helices, 6 helix-helix interactions, 41 beta turns, and 4 gamma turns (4).           F 1,6-BPase is a tetrameric enzyme of four identical subunits each of 337 amino acid residues and molecular weight of about 36,500 Daltons. On each subunit is an active site for the substrate (2FP), 28 Angstroms away from the active site is an AMP binding site, and a metal binding site lies between these two domains (5). The four subunits of F 1,6-BPase are labeled from upper left to right (clockwise) C1, C2, C3, and C4 respectively. C1 and C2 correspond to the upper dimer while C3 and C4 correspond to the lower dimer. The tertiary structure of each subunit is divided into two domains, the AMP domain (residues 1–200) and the F 1,6-bisphosphate domain (residues 201–337). The AMP domain has the AMP binding site at the C1–C4 interface and the Fructose 1,6 bisphosphate domain contains the active site at the C1–C2 interface (6). Figure 2. Crystal structure of the fructose 1,6-bisphosphatase (Biological molecule unit) of Sulfolobus tokodaii.  Nishimasu H. et al. RCSB Protein Data Bank. Figure 3. Crystal structure of the fructose 1,6-bisphosphatase (Asymmetrical unit) of Sulfolobus tokodaii.  Nishimasu H. et al. RCSB Protein Data Bank