title: Specificity determinants in inositol polyphosphate synthesis: crystal structure of inositol 1,3,4-trisphosphate 5/6-kinase.
abstract: Inositol hexakisphosphate and other inositol high polyphosphates have diverse and critical roles in eukaryotic regulatory pathways. Inositol 1,3,4-trisphosphate 5/6-kinase catalyzes the rate-limiting step in inositol high polyphosphate synthesis in animals. This multifunctional enzyme also has inositol 3,4,5,6-tetrakisphosphate 1-kinase and other activities. The structure of an archetypal family member, from Entamoeba histolytica, has been determined to 1.2 A resolution in binary and ternary complexes with nucleotide, substrate, and product. The structure reveals an ATP-grasp fold. The inositol ring faces ATP edge-on such that the 5- and 6-hydroxyl groups are nearly equidistant from the ATP gamma-phosphate in catalytically productive phosphoacceptor positions and explains the unusual dual site specificity of this kinase. Inositol tris- and tetrakisphosphates interact via three phosphate binding subsites and one solvent-exposed site that could in principle be occupied by 18 different substrates, explaining the mechanisms for the multiple specificities and catalytic activities of this enzyme.
authors.affiliation: Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, United States Department of Health and Human Services, Bethesda, Maryland 20892, USA.
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Miller
authors.forename: Monita P
authors.initials: MP
authors.lastname: Wilson
authors.forename: Philip W
authors.initials: PW
authors.lastname: Majerus
authors.forename: James H
authors.initials: JH
authors.lastname: Hurley
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004252:DNA Mutational Analysis; D004583:Electrons; D004748:Entamoeba histolytica / Q000737:chemistry; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D008024:Ligands; D008274:Magnesium / Q000378:metabolism; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D015394:Molecular Structure; D016297:Mutagenesis, Site-Directed; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D018411:Spodoptera / Q000166:cytology; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D007295:Inositol Phosphates; D008024:Ligands; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; C058097:inositol 1,3,4-trisphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C056875:myo-inositol-trisphosphate 6-kinase; D008274:Magnesium