Investigation of the Structural Stability of hUBF HMG Box 5 by Native-State Hydrogen Exchange
详细信息 查看全文
- 作者：Dandan Wang ; Jiahai Zhang ; Xianju Jin ; Jihui Wu ; Yunyu Shi
- 刊名：Biochemistry
- 出版年：2007
- 出版时间：February 6, 2007
- 年：2007
- 卷：46
- 期：5
- 页码：1293 - 1302
- 全文大小：330K
- 年卷期：v.46,no.5(February 6, 2007)
- ISSN：1520-4995
文摘
HMG box 5 of human upstream binding factor (hUBF) consists of three 
-helices arrangedin an L-shape with a hydrophobic core embraced by these helices and stabilized by extensive hydrophobicinteractions between nonpolar residues around the core. The GdmCl-induced equilibrium unfoldingtransition of HMG box 5 of hUBF was monitored by both circular dichroism (CD) and fluorescencespectra. A cooperative two-state unfolding process was observed. The unfolding free energy, 
GU(D2O),and the cooperativity of the unfolding reaction, m, are 4.6 ± 0.16 kcal·mol-1 and 1.62 ± 0.06kcal·mol-1·M-1, respectively. Native-state hydrogen exchange (NHX) experiments under EX2 conditionswere performed. NHX results clearly show that the hydrophobic core among the three helices is a slow-exchange core. The three helices would not contribute equally to the stability of the native protein. Helix3 appears to contribute the least to the stability. The NHX data have also allowed the local, subglobal,and global unfolding structures of hUBF HMG box 5 to be dissected, and common global and subglobalunfolding units were successfully detected.
-helices arrangedin an L-shape with a hydrophobic core embraced by these helices and stabilized by extensive hydrophobicinteractions between nonpolar residues around the core. The GdmCl-induced equilibrium unfoldingtransition of HMG box 5 of hUBF was monitored by both circular dichroism (CD) and fluorescencespectra. A cooperative two-state unfolding process was observed. The unfolding free energy, GU(D2O),and the cooperativity of the unfolding reaction, m, are 4.6 ± 0.16 kcal·mol-1 and 1.62 ± 0.06kcal·mol-1·M-1, respectively. Native-state hydrogen exchange (NHX) experiments under EX2 conditionswere performed. NHX results clearly show that the hydrophobic core among the three helices is a slow-exchange core. The three helices would not contribute equally to the stability of the native protein. Helix3 appears to contribute the least to the stability. The NHX data have also allowed the local, subglobal,and global unfolding structures of hUBF HMG box 5 to be dissected, and common global and subglobalunfolding units were successfully detected.