title: Crystal structure of a purine/pyrimidine phosphoribosyltransferase-related protein from Thermus thermophilus HB8.
abstract: Adenine phosphoribosyltransferase (APRTase) is a widely distributed enzyme involved in the salvage of adenine to form an adenine nucleotide. We crystallized and determined the X-ray crystallographic structure of a purine/pyrimidine phosphoribosyltransferase-related protein from the thermophilic bacterium, Thermus thermophilus HB8. The crystal space group was C2 with unit cell dimensions of a = 167.42 A, b = 61.41 A, c = 102.39 A, beta = 94.0 degrees . Initial phases were determined to 2.6 A using the multiple wavelength anomalous dispersion method and selenomethionine substituted protein (Se-MAD), and refined using a 1.9 A "native" data set. The asymmetric unit contains two pairs of identical dimers, each related by noncrystallographic two-fold symmetry. The fifth monomer forms a similar dimer across a crystallographic two-fold axis. These dimers appear to be the biological unit with both monomers contributing to an unusual highly charged arginine-rich bridge region separating the two active sites. Comparison with distantly related APRTases reveal similarities and differences of the active site.
authors.affiliation: RIKEN Harima Institute, Hyogo, Japan.
authors.forename: Peter H
authors.initials: PH
authors.lastname: Rehse
authors.forename: Tahir H
authors.initials: TH
authors.lastname: Tahirov
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine / Q000737:chemistry; D001665:Binding Sites; D003460:Crystallization; D018360:Crystallography, X-Ray; D008969:Molecular Sequence Data; D010430:Pentosyltransferases / Q000737:chemistry*; D017433:Protein Structure, Secondary; D011687:Purines / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D016963:Thermus thermophilus / Q000737:chemistry* / Q000201:enzymology*
chemical_list: D011687:Purines; D001120:Arginine; D010430:Pentosyltransferases; C022500:pyrimidine phosphoribosyltransferase; C030985:purine