Schumann Wolfgang
Institute of Genetics, University of Bayreuth, D-95440 Bayreuth, Germany.
J Biosci. 2007 Apr;32(3):549-57. doi: 10.1007/s12038-007-0054-8.
Temperature is an important physical stress factor sensed by bacteria and used to regulate gene expression. Three different macromolecules have been identified being able to sense temperature: DNA, mRNA and proteins. Depending on the induction mechanism, two different pathways have to be distinguished, namely the heat shock response and the high temperature response. While the heat shock response is induced by temperature increments and is transient, the high temperature response needs a specific temperature to become induced and proceeds as long as cells are exposed to that temperature. The heat shock response is induced by denatured proteins and aimed to prevent formation of protein aggregates by refolding or degradation, and the high temperature response is mainly used by pathogenic bacteria to detect entry into a mammalian host followed by induction of their virulence genes. All known high temperature sensors are present in two alternative conformations depending on the temperature. Heat shock sensors are either molecular chaperones or proteases which keep either a positive transcriptional regulator inactive or a negative regulator active or do not attack the regulator, respectively, under physiological conditions. Denatured proteins either titrate the molecular chaperones or activate the protease. The evolution of the different temperature sensors is discussed.
温度是细菌能够感知的重要物理应激因素，并用于调节基因表达。已确定三种不同的大分子能够感知温度：DNA、mRNA和蛋白质。根据诱导机制，必须区分两种不同的途径，即热休克反应和高温反应。热休克反应由温度升高诱导且是短暂的，而高温反应需要特定温度才能被诱导，并且只要细胞暴露于该温度就会持续进行。热休克反应由变性蛋白质诱导，旨在通过重折叠或降解来防止蛋白质聚集体的形成，而高温反应主要被病原菌用于检测进入哺乳动物宿主并随后诱导其毒力基因。所有已知的高温传感器根据温度呈现两种不同的构象。热休克传感器要么是分子伴侣要么是蛋白酶，它们在生理条件下分别使正向转录调节因子失活、使负向调节因子激活或不攻击调节因子。变性蛋白质要么滴定分子伴侣要么激活蛋白酶。文中还讨论了不同温度传感器的进化。
