HtrA蛋白酶属于胞质外蛋白质质量控制系统，它们通过发挥蛋白酶和分子伴侣功能来去除错误折叠和错误定位的蛋白质以维持细胞的胞质外蛋白质稳态。基因组数据显示HtrA蛋白酶广泛存在于细菌、古菌和真核生物中。细菌HtrA蛋白酶与细菌的抗逆性和致病性等密切相关，真核生物HtrA蛋白酶参与细胞增殖、凋亡、自噬及光合器的维持等重要生物学过程。但迄今为止，古菌HtrA蛋白酶的生理功能和作用机制依然未知。本项目以嗜盐古菌Natrinema sp. J7-2的三种HtrA蛋白酶为研究对象，研究它们的基本生化性质、活化机制和环境胁迫响应机制，比较分析三种酶在这些方面的作用特点、差异和分子机制，重点阐明HtrA蛋白酶在嗜盐古菌中的生理功能和作用机理并探寻其中所蕴含的规律，在理论上为三域生命形式中普遍存在的胞质外蛋白质质量控制系统的运行机制提供新见解，丰富和深化人们对古菌生命特征及环境适应性的认识。

HtrA (high temperature requirement A) proteases belong to extracytoplasmic protein quality control system. By virtue of their protease and chaperone activities, HtrA proteases remove misfolded or mislocalized proteins to maintain protein homeostasis in extracytoplasmic space of living cells. Genomic analysis reveals that HtrA proteases are widely distributed in bacteria, archaea, and eukarya. It is well known that HtrA proteases contribute to stress resistance and pathogenesis of bacteria, and are involved in important cellular processes in eukarya, including cell proliferation, apoptosis, autophagy, and maintenance of the photosynthetic apparatus. However, the physiological roles and molecular mechanisms of archaeal HtrA proteases remain unknown. In this research project, three HtrA proteases of haloarchaeon Natrinema sp. J7-2 will be characterized in terms of their biochemical properties, activation mechanisms, and environmental stress response mechanisms. Meanwhile, the molecular basis for differences in enzymatic properties between the enzymes will also be investigated. Moreover, the physiological roles and mechanisms of the three haloarchaeal HtrA proteases will be investigated in vivo. The results of this study will not only provide new insight into HtrA proteases, the extracytoplasmic protein quality control system conserved in the three domains of life, but will also deepen our understanding of biological characteristics and adaptation mechanism of haloarchaea.