Watson K
Department of Biochemistry, Microbiology and Nutrition, University of New England, Armidale, Australia.
Adv Microb Physiol. 1990;31:183-223. doi: 10.1016/s0065-2911(08)60122-8.
There is general agreement that a function, perhaps the major function, of stress proteins under normal physiological conditions is to help assembly and disassembly of protein complexes and to catalyse protein-translocation processes. It remains unclear, however, as to what role these processes play in stressed cells. It could be that cells under stress produce abnormal, misfolded or otherwise damaged proteins and that increased synthesis of stress proteins is required to counter protein modifications. A role for stress proteins in recovery of cells from stress, as opposed to a role in helping cells to withstand a lethal stress, is thus suggested. The intracellular location of stress proteins, in the unstressed and stressed cell, is worthy of further studies. Members of the hsp70 family are associated with the cytosol, mitochondria and endoplasmic reticulum. There is evidence, particularly from studies on mammalian cells (Tanguay, 1985; Welch and Mizzen, 1988; Arrigo et al., 1988), that following stress hsps migrate to various cellular compartments and subsequently delocalize after stress. However, there is little comparable data from microbial systems for this phenomenon (e.g. Rossi and Lindquist, 1989). The question as to the role of stress proteins in the transient acquisition of thermotolerance remains to be answered. It is insufficient to equate the kinetics of stress-protein synthesis with acquisition of thermotolerance. Quantitative data on the amount of stress protein present at various times, including the recovery period, is required. The demonstration that microbial stress proteins are important antigenic determinants of micro-organisms causing major debilitating diseases in the world is an exciting observation. Studies on the interplay of pathogen and host, both carrying similar antigenic hsp determinants, will be a challenging area for future research. It is likely that E. coli and Sacch. cerevisiae, with their well-established biochemical and genetic properties, will continue to be the experimental systems of choice for studies on stress proteins. On the other hand, it is encouraging that studies on other micro-organisms have expanded in the past few years and have made substantial contributions towards our understanding of the stress response. The ubiquitous nature of the stress response and the remarkable evolutionary conservation of the stress proteins continue to be attractive areas for research.
人们普遍认为，在正常生理条件下，应激蛋白的一个功能，或许也是其主要功能，是帮助蛋白质复合物的组装与拆卸，并催化蛋白质转运过程。然而，这些过程在应激细胞中发挥何种作用仍不清楚。可能是应激状态下的细胞会产生异常、错误折叠或其他形式受损的蛋白质，因此需要增加应激蛋白的合成来对抗蛋白质修饰。由此推测，应激蛋白在细胞从应激状态恢复过程中发挥作用，而非帮助细胞抵御致命应激。应激蛋白在未受应激和受应激细胞中的细胞内定位值得进一步研究。热休克蛋白70家族成员与胞质溶胶、线粒体和内质网相关。有证据表明，特别是来自对哺乳动物细胞的研究（坦圭，1985年；韦尔奇和米曾，1988年；阿里戈等人，1988年），应激后热休克蛋白会迁移至细胞的各个区室，随后在应激后发生移位。然而，关于这种现象，微生物系统中几乎没有可比数据（例如，罗西和林德奎斯特，1989年）。应激蛋白在热耐受性短暂获得过程中的作用问题仍有待解答。仅将应激蛋白合成的动力学等同于热耐受性的获得是不够的。需要关于包括恢复期在内的不同时间点存在的应激蛋白量的定量数据。微生物应激蛋白是导致世界上主要使人衰弱疾病的微生物的重要抗原决定簇，这一发现令人兴奋。对携带相似抗原性热休克蛋白决定簇的病原体与宿主之间相互作用的研究将是未来研究的一个具有挑战性的领域。大肠杆菌和酿酒酵母具有成熟的生化和遗传特性，很可能仍将是应激蛋白研究的首选实验系统。另一方面，令人鼓舞的是，过去几年对其他微生物的研究有所扩展，并为我们理解应激反应做出了重大贡献。应激反应的普遍性以及应激蛋白显著的进化保守性仍然是有吸引力的研究领域。
