Molecular Structure of Fructose-1,6-bisphosphatase at 2.8- angstrom Resolution

Fructose-1,6-bisphosphatase (D-fructose-1,6-bisphosphate 1-phosphohydrolase, EC 3.1.3.11) from the cortex of pig kidney and its complexes with either fructose 2,6-bisphosphate (Fru-2,6-P2) or adenosine monophosphate (AMP) have been crystallized in the space group P3(2)21. The three-dimensional structure of the native enzyme has been solved at 3.0-A resolution by the multiple isomorphous replacement method and refined at 2.8-A resolution to a crystallographic R factor of 0.194. A total of 316 of 335 residues, omitting disordered regions 1-5 and 54-67, have been built into the monomer, which has average dimensions of about 30 A by 50 A by 35 A. Four monomeric units aggregate into a molecular tetramer with D2 symmetry, which approximates a disk about 35 A thick. Each monomer consists of about 33% alpha-helix, 23% beta-strand, and 6% beta-turn. Four sites for Fru-2,6-P2 and two major sites for AMP binding per tetramer have been identified by difference Fourier techniques. The binding site for Fru-2,6-P2 is shared by two neighboring monomers and consists of side-chain atoms of Asn-212, Tyr-244, Tyr-264, and Lys-274; backbone atoms of Gly-246 through Met-248; and only Arg-243 from the adjacent subunit. In addition, Asn-125, Tyr-215, and Lys-269 are located within a distance of about 5 A of Fru-2,6-P2. A negatively charged pocket near this binding site includes Asp-118, Asp-121, Glu-280, Glu-97, and Glu-98. The AMP binding site is located near Val-17, Gln-20, Gly-21, Ala-24 through Met-30, Lys-112, Tyr-113, Arg-140, and Met-177.