title: Proteolytic footprinting of vaccinia topoisomerase bound to DNA.
abstract: Vaccinia DNA topoisomerase, a member of the eukaryotic type I enzyme family, binds duplex DNA and forms a covalent protein.DNA complex at sites containing a conserved sequence element 5'-CCCTT decreases. The structure of the enzyme in the free and DNA-bound states was probed by limited proteolysis. The free topoisomerase (a 314-amino acid polypeptide) consists of protease-resistant amino- and carboxyl-terminal structural domains flanking a protease-sensitive "hinge." The hinge region, located between residues 135 and 142, is defined by accessibility to three different proteases. The amino-terminal region is punctuated by a trypsin-sensitive "bridge" at Arg-80, suggesting at least a tripartite domain structure overall. A specific subset of residues accessible to proteases in the free enzyme becomes resistant to proteolysis in the DNA-bound state. The trypsin-sensitive site at Arg-80 is protected almost completely in the covalent complex. Within the hinge region, Lys-135, Tyr-136, and Glu-139 are protected from trypsin, chymotrypsin, and V8, respectively. Acquisition of altered protease sensitivity upon DNA binding occurs prior to covalent adduct formation. The 20-kDa carboxyl domain by itself binds noncovalently to duplex DNA, albeit without the sequence specificity characteristic of the full-sized topoisomerase.
authors.affiliation: Molecular Biology Program, Sloan-Kettering Institute, New York, New York 10021, USA.
authors.forename: J
authors.initials: J
authors.lastname: Sekiguchi
authors.forename: S
authors.initials: S
authors.lastname: Shuman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002918:Chymotrypsin; D003001:Cloning, Molecular; D017124:Conserved Sequence; D004247:DNA / Q000737:chemistry* / Q000378:metabolism*; D004264:DNA Topoisomerases, Type I / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D014616:Vaccinia virus / Q000201:enzymology*
chemical_list: D009838:Oligodeoxyribonucleotides; D010446:Peptide Fragments; D011994:Recombinant Proteins; D004247:DNA; D002918:Chymotrypsin; D004264:DNA Topoisomerases, Type I