四聚体
热稳定性
生物素
合作性
化学
亲和素
结晶学
吸热
链霉亲和素
热稳定性
变性(裂变材料)
嗜热菌
差示扫描量热法
生物化学
核化学
热力学
有机化学
酶
基因
物理
大肠杆菌
作者
Martı́n González,Carlos E. Argaraña,Gerardo D. Fidelio
出处
期刊:Biomolecular Engineering
日期:1999-12-01
卷期号:16 (1-4): 67-72
被引量:168
标识
DOI:10.1016/s1050-3862(99)00041-8
摘要
The effect of biotin binding on the thermal stability of streptavidin (STV) and avidin (AVD) was evaluated using differential scanning calorimetry. Biotin binding increases the midpoint of temperature Tm of thermally induced denaturation of STV and AVD in phosphate buffer from 75 and 83 degrees C to 112 and 117 degrees C at full biotin saturation, respectively. This thermostability is the highest reported for proteins coming from either mesophilic or thermophilic organisms. In both proteins, biotin also increases the calorimetric enthalpy and the cooperativity of the unfolding. Thermal stability of STV was also evaluated in the presence of high concentrations of urea or guanidinium hydrochloride (GuHCl). In 6 M GuHCl, STV remains as a tetramer and the Tm of the STV-biotin complex is centered at 108 degrees C, a few degrees below the value obtained in phosphate buffer. On the contrary, STV under fully saturating condition remains mainly in its dimeric form in 8 M urea and the thermogram shows two endotherms. The main endotherm at a lower temperature has been ascribed to the dimeric liganded state with a Tm of 87 degrees C, and the higher temperature endotherm to the tetrameric liganded form with a Tm of 106 degrees C. As the thermostability of unliganded protein in the presence of urea is unchanged upon binding we related the extremely high thermal stability of this protein to both an increase in structural ordering and compactness with the preservation of the tetramer integrity.
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