title: E. coli DNA binding protein HU forms nucleosomelike structure with circular double-stranded DNA.
abstract: The incubation of the E coli DNA binding protein HU with relaxed circular SV40 DNA in the presence of pure nicking-closing enzyme introduces up to 18 negative superhelical turns in the DNA molecules as measured by agarose gel electrophoresis. The maximal density of supercoiling is obtained at a HU-DNA mass ratio of 1. Reconstituted DNA-HU complexes prefixed with glutaraldehyde appear as condensed circular structures having an average of 14 "beads" per circular SV40 DNA molecule, with a "bead" diameter of 180 +/- 23 A. The circular SV40 DNA is condensed by a ratio of 2.0-2.5 relative to naked DNA. This is similar to the ratio (2.4) measured for chromatin formed by reassociation of relaxed SV40 DNA with the four core histones.
mesh_terms: D002843:Chromatin / Q000378:metabolism / Q000648:ultrastructure*; D004265:DNA Helicases / Q000378:metabolism*; D004278:DNA, Superhelical / Q000378:metabolism*; D004279:DNA, Viral / Q000378:metabolism; D004720:Endonucleases / Q000378:metabolism; D004926:Escherichia coli; D006657:Histones / Q000378:metabolism; D007526:Isoelectric Point; D008970:Molecular Weight; D013539:Simian virus 40; D013329:Structure-Activity Relationship
chemical_list: D002843:Chromatin; D004278:DNA, Superhelical; D004279:DNA, Viral; D006657:Histones; D004720:Endonucleases; D004265:DNA Helicases