title: DNA topoisomerase and recombinase activities in Nae I restriction endonuclease.
abstract: Nae I endonuclease must bind to two DNA sequences for cleavage. Examination of the amino acid sequence of Nae I uncovered similarity to the active site of human DNA ligase I, except for leucine 43 in Nae I instead of the lysine essential for ligase activity. Changing leucine 43 to lysine 43 (L43K) changed Nae I activity: Nae I-L43K relaxed supercoiled DNA to yield DNA topoisomers and recombined DNA to give dimeric molecules. Interruption of the reactions of Nae I and Nae I-L43K with DNA demonstrated transient protein-DNA covalent complexes. These findings imply coupled endonuclease and ligase domains and link Nae I endonuclease to the topoisomerase and recombinase protein families.
authors.affiliation: Lineberger Comprehensive Cancer Center, Department of Biochemistry and Biophysics, University of North Carolina Medical School, Chapel Hill 27599.
authors.forename: K
authors.initials: K
authors.lastname: Jo
authors.forename: M D
authors.initials: MD
authors.lastname: Topal
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D004254:DNA Nucleotidyltransferases / Q000378:metabolism*; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004270:DNA, Circular / Q000378:metabolism; D015252:Deoxyribonucleases, Type II Site-Specific / Q000737:chemistry / Q000378:metabolism*; D019426:Integrases; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D045522:Recombinases; D017386:Sequence Homology, Amino Acid
chemical_list: D004270:DNA, Circular; D045522:Recombinases; D004254:DNA Nucleotidyltransferases; D019426:Integrases; C115006:integron integrase IntI1; C060630:endodeoxyribonuclease NaeI; D015252:Deoxyribonucleases, Type II Site-Specific; D004264:DNA Topoisomerases, Type I