Premium
Elongational flow studies on conformational change in DNA induced by DNA‐binding protein HU
Author(s) -
Endoh Takashi,
Iyaguchi Daisuke,
Sasaki Naoki,
Tanaka Isao,
Nakata Mitsuo
Publication year - 2003
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.10346
Subject(s) - chemistry , dna , conformational change , biophysics , biochemistry , biology
Interaction of DNA‐binding protein HU from Bacillus stearothermophilis (HUBst) with coliphage T2 DNA was investigated by observing an elongational flow‐induced birefringence, Δ n , 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 Δ n had a critical strain rate ϵ˙ c for the appearance of flow birefringence at all of the HU concentrations examined, indicating that a coil–stretch transition occurred at ϵ˙ c in each DNA–HU system. For strain rates larger than ϵ˙ c , Δ n increased rapidly and then gradually, approaching a plateau value. The value of ϵ˙ c increased with an increase in HU concentration. Analysis based on the relationship between ϵ˙ c and the Rouse–Zimm relaxation time revealed that the increase in ϵ˙ c with increase in HU can be explained by the decrease in the size of the DNA–HU complex. The plateau birefringence value, Δ n p , decreased at small HU concentrations but did not change at larger HU concentrations. Considering that Δ n 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. © 2003 Wiley Periodicals, Inc. Biopolymers 68: 486–496, 2003