title: Crystal structure of NaeI-an evolutionary bridge between DNA endonuclease and topoisomerase.
abstract: NAE:I is transformed from DNA endonuclease to DNA topoisomerase and recombinase by a single amino acid substitution. The crystal structure of NAE:I was solved at 2.3 A resolution and shows that NAE:I is a dimeric molecule with two domains per monomer. Each domain contains one potential DNA recognition motif corresponding to either endonuclease or topoisomerase activity. The N-terminal domain core folds like the other type II restriction endonucleases as well as lambda-exonuclease and the DNA repair enzymes MutH and Vsr, implying a common evolutionary origin and catalytic mechanism. The C-terminal domain contains a catabolite activator protein (CAP) motif present in many DNA-binding proteins, including the type IA and type II topoisomerases. Thus, the NAE:I structure implies that DNA processing enzymes evolved from a few common ancestors. NAE:I may be an evolutionary bridge between endonuclease and DNA processing enzymes.
authors.affiliation: Department of Biochemistry and Biophysics and Lineberger Comprehensive Cancer Center, The University of North Carolina, Chapel Hill, NC 27599-7260, USA.
authors.forename: Q
authors.initials: Q
authors.lastname: Huai
authors.forename: J D
authors.initials: JD
authors.lastname: Colandene
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
authors.forename: F
authors.initials: F
authors.lastname: Luo
authors.forename: Y
authors.initials: Y
authors.lastname: Zhao
authors.forename: M D
authors.initials: MD
authors.lastname: Topal
authors.forename: H
authors.initials: H
authors.lastname: Ke
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry; D001665:Binding Sites; D002384:Catalysis; D020134:Catalytic Domain; D003461:Crystallography; D004264:DNA Topoisomerases, Type I / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000737:chemistry; D015252:Deoxyribonucleases, Type II Site-Specific / Q000737:chemistry*; D004706:Endodeoxyribonucleases / Q000145:classification; D019143:Evolution, Molecular; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020836:Protein Structure, Quaternary; D017356:Synchrotrons
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D004706:Endodeoxyribonucleases; C060630:endodeoxyribonuclease NaeI; D015252:Deoxyribonucleases, Type II Site-Specific; D004264:DNA Topoisomerases, Type I