title: 2.1 A structure of Serratia endonuclease suggests a mechanism for binding to double-stranded DNA.
abstract: The crystal structure of Serratia endonuclease has been solved to 2.1 A by multiple isomorphous replacement. This magnesium-dependent enzyme is equally active against single- and double-stranded DNA, as well as RNA, without any apparent base preference. The Serratia endonuclease fold is distinct from that of other nucleases that have been solved by X-ray diffraction. The refined structure consists of a central layer containing six antiparallel beta-strands which is flanked on one side by a helical domain and on the opposite side by one dominant helix and a very long coiled loop. Electrostatic calculations reveal a strongly polarized molecular surface and suggest that a cleft between this long helix and loop, near His 89, may contain the active site of the enzyme.
authors.affiliation: Department of Biochemical and Biophysical Sciences, University of Houston, Texas 77204-5934, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Miller
authors.forename: J
authors.initials: J
authors.lastname: Tanner
authors.forename: M
authors.initials: M
authors.lastname: Alpaugh
authors.forename: M J
authors.initials: MJ
authors.lastname: Benedik
authors.forename: K L
authors.initials: KL
authors.lastname: Krause
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D018360:Crystallography, X-Ray; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism*; D004706:Endodeoxyribonucleases / Q000737:chemistry* / Q000378:metabolism*; D004722:Endoribonucleases / Q000737:chemistry* / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012706:Serratia marcescens / Q000201:enzymology*
chemical_list: D004269:DNA, Bacterial; D004706:Endodeoxyribonucleases; D004722:Endoribonucleases; C021835:Serratia marcescens nuclease; D008274:Magnesium