title: Stabilization due to dimer formation of phosphoribosyl anthranilate isomerase from Thermus thermophilus HB8: X-ray Analysis and DSC experiments.
abstract: The crystal structure of phosphoribosyl anthranilate isomerase (PRAI) from Thermus thermophilus HB8 (TtPRAI) was solved at 2.0 A resolution. The overall structure of TtPRAI with a dimeric structure was quite similar to that of PRAI from Thermotoga maritima (TmPRAI). In order to elucidate the stabilization mechanism of TtPRAI, its physicochemical properties were examined using DSC, CD, and analytical centrifugation at various pHs in relation to the association-dissociation of the subunits. Based on the experimental results for TtPRAI and the structural information on TtPRAI and TmPRAI, we found that: (i) the denaturation of TtPRAI at acidic pH is correlated with the dissociation of its dimeric form; (ii) the hydrophobic interaction of TtPRAI in the monomer structure is slightly greater than that of TmPRAI, but dimer interface of the TmPRAI is remarkably greater; (iii) the contributions of hydrogen bonds and ion bonds to the stability are similar to each other; and (iv) destabilization due to the presence of cavities in TtPRAI is greater than that of TmPRAI in both the monomer and dimer structures.
authors.affiliation: RIKEN Harima Institute at SPring8, 1-1-1 Kohto, Mikazukicho, Sayo, Hyogo 679-5148.
authors.forename: Junichiro
authors.initials: J
authors.lastname: Taka
authors.forename: Kyoko
authors.initials: K
authors.lastname: Ogasahara
authors.forename: Jeyaraman
authors.initials: J
authors.lastname: Jeyakanthan
authors.forename: Naoki
authors.initials: N
authors.lastname: Kunishima
authors.forename: Chizu
authors.initials: C
authors.lastname: Kuroishi
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Sugahara
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Yokoyama
authors.forename: Katsuhide
authors.initials: K
authors.lastname: Yutani
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000737:chemistry*; D000595:Amino Acid Sequence; D001665:Binding Sites; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D019281:Dimerization; D004795:Enzyme Stability; D004926:Escherichia coli / Q000201:enzymology; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020836:Protein Structure, Quaternary; D016415:Sequence Alignment; D013824:Thermus / Q000201:enzymology; D016963:Thermus thermophilus / Q000201:enzymology*
chemical_list: D019747:Aldose-Ketose Isomerases; C029865:phosphoribosylanthranilate isomerase