title: Crystallization and preliminary X-ray characterization of two thermostable DNA nucleases.
abstract: Temperature-tolerant organisms are an important source to enhance the stability of enzymes used in biotechnological processes. The DNA-cleaving enzyme exonuclease III from Escherichia coli is used in several applications in gene technology. A thermostable variant could expand the applicability of the enzyme in these methods. Two homologous nucleases from Archaeoglobus fulgidus (ExoAf) and Methanothermobacter thermoautrophicus (ExoMt) were studied for this purpose. Both enzymes were crystallized in different space groups using (poly)ethylene glycols, 2,4-methyl pentandiol, dioxane, ethanol or 2-propanol as precipitants. The addition of a 10-mer DNA oligonucleotide was important to obtain monoclinic crystals of ExoAf and ExoMt that diffracted to resolutions better than 2 A using synchrotron radiation. The crystal structures of the homologous proteins can serve as templates for genetic engineering of the E. coli exonuclease III and will aid in understanding the different catalytic properties of the enzymes.
authors.affiliation: Center for Biotechnology and Biomedicine, Institute for Bioanalytical Chemistry, Faculty of Chemistry and Mineralogy, University of Leipzig, Deutscher Platz 5, 04103 Leipzig, Germany.
authors.forename: E Bartholomeus
authors.initials: EB
authors.lastname: Kuettner
authors.forename: Sven
authors.initials: S
authors.lastname: Pfeifer
authors.forename: Antje
authors.initials: A
authors.lastname: Keim
authors.forename: Thomas
authors.initials: T
authors.lastname: Greiner-Stöffele
authors.forename: Norbert
authors.initials: N
authors.lastname: Sträter
mesh_terms: D019611:Archaeoglobus fulgidus / Q000201:enzymology*; D003460:Crystallization; D018360:Crystallography, X-Ray; D004795:Enzyme Stability; D005090:Exodeoxyribonucleases / Q000737:chemistry*; D006358:Hot Temperature; D017013:Methanobacteriaceae / Q000201:enzymology*
chemical_list: D005090:Exodeoxyribonucleases; C020133:exodeoxyribonuclease III