title: Elongational flow studies on conformational change in DNA induced by DNA-binding protein HU.
abstract: Interaction of DNA-binding protein HU from Bacillus stearothermophilis (HUBst) with coliphage T2 DNA was investigated by observing an elongational flow-induced birefringence, Deltan, of a T2-phage DNA aqueous solution at various HU concentrations. Localized flow birefringence was observed in the pure elongational flow region, and the strain rate dependence of Deltan had a critical strain rate epsilon;(c) for the appearance of flow birefringence at all of the HU concentrations examined, indicating that a coil-stretch transition occurred at epsilon;(c) in each DNA-HU system. For strain rates larger than epsilon;(c), Deltan increased rapidly and then gradually, approaching a plateau value. The value of epsilon;(c) increased with an increase in HU concentration. Analysis based on the relationship between epsilon; (c) and the Rouse-Zimm relaxation time revealed that the increase in epsilon;(c)with increase in HU can be explained by the decrease in the size of the DNA-HU complex. The plateau birefringence value, Deltan(p), decreased at small HU concentrations but did not change at larger HU concentrations. Considering that Deltan(p) is related to the orientational order parameter of segments, it was concluded that there were at least two stages in the process of compaction of DNA induced by HU.
authors.affiliation: Division of Biological Sciences, Graduate School of Science, Hokkaido University, Kita-ku, Sapporo 060-0810, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Endoh
authors.forename: Daisuke
authors.initials: D
authors.lastname: Iyaguchi
authors.forename: Naoki
authors.initials: N
authors.lastname: Sasaki
authors.forename: Isao
authors.initials: I
authors.lastname: Tanaka
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Nakata
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D001718:Birefringence; D004247:DNA / Q000737:chemistry* / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D001411:Geobacillus stearothermophilus; D007700:Kinetics; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D014157:Transcription Factors; C040330:histone-like protein HU, bacteria; D004247:DNA