title: Nucleotide binding by the synapse associated protein SAP90.
abstract: The rat synapse associated protein SAP90 is a member of a superfamily of potential guanylate kinases localized at cell-cell contact sites. This superfamily includes the synapse associated protein SAP97, a close relative of SAP90, the Drosophila tumor suppressor gene product dlg-Ap, the mammalian zonula occludens proteins ZO-1 and ZO-2 and the erythrocyte protein p55. Here we show that SAP90 specifically binds GMP in the micromolar range while binding to ATP, GDP and ADP is at a much lower affinity (10-25 mM), whether or not binding is detected for other guanine and adenine nucleotides. No guanylate kinase activity of SAP90 was detected under our experimental conditions. The importance of the GMP binding capacity per se and an evolutionary role for conserving of the guanylate kinase domain in this superfamily are discussed.
authors.affiliation: Department of Biological Chemistry, Hebrew University, Jerusalem, Israel.
authors.forename: U
authors.initials: U
authors.lastname: Kistner
authors.forename: C C
authors.initials: CC
authors.lastname: Garner
authors.forename: M
authors.initials: M
authors.lastname: Linial
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D006157:Guanosine Monophosphate / Q000378:metabolism; D051528:Guanylate Kinases; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009703:Nucleoside-Phosphate Kinase / Q000378:metabolism; D009711:Nucleotides / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D000074407:SAP90-PSD95 Associated Proteins; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D017386:Sequence Homology, Amino Acid
chemical_list: D009419:Nerve Tissue Proteins; D009711:Nucleotides; D011994:Recombinant Proteins; D000074407:SAP90-PSD95 Associated Proteins; D006157:Guanosine Monophosphate; D000255:Adenosine Triphosphate; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases