Obuchi K, Iwahashi H, Lepock J R, Komatsu Y
National Institute of Bioscience and Human-technology, AIST, Ibaraki, Japan.
Yeast. 1998 Oct;14(14):1249-55. doi: 10.1002/(SICI)1097-0061(1998100)14:14<1249::AID-YEA323>3.0.CO;2-A.
Hyperthermic cell killing profiles of Saccharomyces cerevisiae cells were biphasic and a shoulder (phase 1) was followed by an exponential killing (phase 2). Assuming that (i) the rate of thermal damage in particular macromolecules or their assemblies limits the rate of hyperthermic cell killing (the critical target model), and (ii) the damages of two families of targets are lethal independently, we built a 'dual critical target model' in order to interpret the biphasic cell killing. Time-courses of temperature-programmed fractional survival were traced for S. cerevisiae cells in exponentially growing phase, heat shocked, and in stationary phase. Non-linear curve-fitting of the time-courses by using the dual critical target model provided the Arrhenius parameters of denaturation of the two families of targets. The cells were killed more slowly in phase 1 than in phase 2. Arrest in stationary phase, not heat shock, stabilizes the family of targets that is critical to phase 1 death. On the other hand, both heat-shock response and arrest in stationary phase stabilizes the other family of targets that, in addition to the previous one, is responsible for phase 2 death.
酿酒酵母细胞的热致细胞杀伤曲线呈双相，先是一个平台期（阶段1），随后是指数杀伤期（阶段2）。假设（i）特定大分子或其聚集体中的热损伤速率限制了热致细胞杀伤速率（关键靶点模型），以及（ii）两类靶点的损伤各自独立导致细胞死亡，我们构建了一个“双关键靶点模型”来解释双相细胞杀伤现象。对处于指数生长期、热激处理以及稳定期的酿酒酵母细胞，追踪了程序升温下细胞存活率随时间的变化过程。用双关键靶点模型对这些时间过程进行非线性曲线拟合，得到了两类靶点变性的阿伦尼乌斯参数。细胞在阶段1的死亡速度比在阶段2慢。细胞停滞于稳定期而非热激处理，可使对阶段1死亡起关键作用的那类靶点稳定。另一方面，热激反应和细胞停滞于稳定期均可使另一类靶点稳定，除前一类靶点外，这后一类靶点也导致阶段2的细胞死亡。
