title: A DNase from the trypanosomatid Crithidia fasciculata.
abstract: We have purified to homogeneity a DNase from a Crithidia fasciculata crude mitochondrial lysate. The enzyme is present in two forms, either as a 32 kDa polypeptide or as a multimer containing the 32 kDa polypeptide in association with a 56 kDa polypeptide. Native molecular weight measurements indicate that these forms are a monomer and possibly an alpha 2 beta 2 tetramer, respectively. The monomeric and multimeric forms of the enzyme are similar in their catalytic activities. Both digest double-stranded DNA about twice as efficiently as single-stranded DNA. They introduce single-strand breaks into a supercoiled plasmid but do not efficiently make double-strand breaks. They degrade a linearized plasmid more efficiently than a nickel plasmid. Both enzymes degrade a 5'-32P-labeled double-stranded oligonucleotide to completion, with the 5'-terminal nucleotide ultimately being released as a 5'-mononucleotide. One difference between the monomeric and multimeric forms of the enzyme, demonstrated by a band shift assay, is that the multimeric form binds tightly to double-stranded DNA, possibly aggregating it.
authors.affiliation: Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Li
authors.forename: K Y
authors.initials: KY
authors.lastname: Hwa
authors.forename: P T
authors.initials: PT
authors.lastname: Englund
mesh_terms: D000818:Animals; D001483:Base Sequence; D002499:Centrifugation, Density Gradient; D002850:Chromatography, Gel; D016831:Crithidia fasciculata / Q000201:enzymology*; D004247:DNA / Q000378:metabolism; D003851:Deoxyribonucleases / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D008928:Mitochondria / Q000201:enzymology*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D004247:DNA; D003851:Deoxyribonucleases