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High activity of Mj hsp16.5 under acidic condition

Science China Chemistry 2009年第3期52卷 325-331页

作者： WANG Zheng CAO AoNeng LAI LuHua Beijing National Laboratory for Molecular Sciences and State Key Laboratory of Structural Chemistry for Stable and Unstable SpeciesCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China Institute of Nanochemistry and Nanobiology Shanghai UniversityShanghai 200444China

Small heat shock proteins (shsps) exist ubiquitously among all organisms, with a variety of functions. All small heat shock proteins assemble into a native large oligomeric state containing 9–40 monomers. The shsps show chaperone-like activity to prevent the aggregation of nonnative proteins under stressful cellular conditions such as non-optimal temperatures, pH changes, osmotic pressure, and exposure to toxic chemicals. It was found that a common dimeric subunit of shsps might be the major active species, but whether the native large oligomeric state is only a storage state or a state crucial to its molecular chaperone activity is still under debate. The native large oligomeric state of the small heat shock protein from a hyperthermophilic methanarchaeon, Methanococcus jannaschii (Mj hsp 16.5), is a stable icositetramer, which is a symmetric hollow sphere that is very stable even at 85°C, and no small active subunit has been detected till now. Our results show that Mj shsp 16.5 changes into small and active oligomeric state at pH 3, likely as octamers (average result) at 25°C, and dimers at 65°C. The dimer of Mj hsp 16.5 at pH 3.0 and 65°C is very active and efficient, even 7-fold more efficient than the high-temperature-activated icositetramer at neutral pH. Monomer exchange can be observed between dimers of Mj hsp 16.5 at pH 3.0 and 65°C. These results not only demonstrate that the icositetramer structure of Mj shsp16.5 is not necessary for its molecular chaperone activity, but also suggest that Mj shsp16.5 is a very efficient chaperone acting at high temperature and under the acidic condition. Even though it is not clear whether the native environment of Methanococcus jannaschii is acidic or not, given its ability to excrete acidic compounds, it is likely that Methanococcus jannaschii will encounter acidic internal or external environments at high temperature. Our results demonstrate that Mj hsp 16.5 may help Methanococcus jannaschii to survive better under tho

关键词： small heat shock protein chaperone Mj hsp16.5 dimer acidic folding aggregation

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小分子热休克蛋白Mj hsp16.5的分级变性

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物理化学学报 2008年第10期24卷 1745-1750页

作者：王铮赖兵曹洁李竹瞿丽丽曹傲能来鲁华北京大学化学与分子工程学院北京分子科学国家实验室分子动态与稳态结构国家重点实验室北京100871 上海大学纳米化学与生物学研究所上海200444

应用荧光光谱、圆二色光谱、体积排阻色谱、激光动态光散射等技术,研究了来自嗜热古细菌Methanococcus jannaschii(Mj)的小分子热休克蛋白Mj hsp16.5在变性剂作用下的变性过程.研究表明,在pH7时,Mj hsp16.5在8mol·L-1尿素作用下不会发... 详细信息

应用荧光光谱、圆二色光谱、体积排阻色谱、激光动态光散射等技术,研究了来自嗜热古细菌Methanococcus jannaschii(Mj)的小分子热休克蛋白Mj hsp16.5在变性剂作用下的变性过程.研究表明,在pH7时,Mj hsp16.5在8mol·L-1尿素作用下不会发生变性.在pH7条件下,盐酸胍对Mj hsp16.5的变性表现为一个分级过程,分别在2.0、3.0和6.0mol·L-1盐酸胍浓度附近,出现明显的结构变化;到7.0mol·L-1盐酸胍时,Mj hsp16.5才完全变性.降低溶液pH值将使Mj hsp16.5的变性变得更为容易.

关键词：小热休克蛋白 Mj hsp16.5 蛋白质折叠变性剂分级变性圆二色谱

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