Weber Michael H, Marahiel Mohamed A
Sci Prog. 2003;86(Pt 1-2):9-75. doi: 10.3184/003685003783238707.
As a measure for molecular motion, temperature is one of the most important environmental factors for life as it directly influences structural and hence functional properties of cellular components. After a sudden increase in ambient temperature, which is termed heat shock, bacteria respond by expressing a specific set of genes whose protein products are designed to mainly cope with heat-induced alterations of protein conformation. This heat shock response comprises the expression of protein chaperones and proteases, and is under central control of an alternative sigma factor (sigma 32) which acts as a master regulator that specifically directs RNA polymerase to transcribe from the heat shock promotors. In a similar manner, bacteria express a well-defined set of proteins after a rapid decrease in temperature, which is termed cold shock. This protein set, however, is different from that expressed under heat shock conditions and predominantly comprises proteins such as helicases, nucleases, and ribosome-associated components that directly or indirectly interact with the biological information molecules DNA and RNA. Interestingly, in contrast to the heat shock response, to date no cold-specific sigma factor has been identified. Rather, it appears that the cold shock response is organized as a complex stimulon in which post-transcriptional events play an important role. In this review, we present a summary of research results that have been acquired in recent years by examinations of bacterial cold shock responses. Important processes such as cold signal perception, membrane adaptation, and the modification of the translation apparatus are discussed together with many other cold-relevant aspects of bacterial physiology and first attempts are made to dissect the cold shock stimulon into less complex regulatory subunits. Special emphasis is placed on findings concerning the nucleic acid-binding cold shock proteins which play a fundamental role not only during cold shock adaptation but also under optimal growth conditions.
作为分子运动的一种度量，温度是对生命而言最重要的环境因素之一，因为它直接影响细胞成分的结构，进而影响其功能特性。在环境温度突然升高（即热休克）后，细菌会通过表达一组特定的基因做出反应，这些基因的蛋白质产物主要用于应对热诱导的蛋白质构象改变。这种热休克反应包括蛋白质伴侣和蛋白酶的表达，并且受一种替代西格玛因子（西格玛32）的中央控制，该因子作为主要调节因子，专门引导RNA聚合酶从热休克启动子进行转录。以类似的方式，细菌在温度快速下降（即冷休克）后会表达一组明确的蛋白质。然而，这组蛋白质与热休克条件下表达的蛋白质不同，主要包括诸如解旋酶、核酸酶和核糖体相关成分等蛋白质，它们直接或间接与生物信息分子DNA和RNA相互作用。有趣的是，与热休克反应不同，迄今为止尚未鉴定出冷特异性西格玛因子。相反，冷休克反应似乎是作为一个复杂的刺激子组织起来的，其中转录后事件起着重要作用。在这篇综述中，我们总结了近年来通过研究细菌冷休克反应所获得的研究结果。讨论了诸如冷信号感知、膜适应和翻译装置修饰等重要过程，以及细菌生理学中许多其他与冷相关的方面，并首次尝试将冷休克刺激子分解为不太复杂的调节亚基。特别强调了关于核酸结合冷休克蛋白的研究结果，这些蛋白不仅在冷休克适应过程中，而且在最佳生长条件下都起着基本作用。
