Damerau K, St John A C
Nelson Biology Laboratories, Department of Biological Sciences, Rutgers University, Piscataway, New Jersey 08855-1059.
J Bacteriol. 1993 Jan;175(1):53-63. doi: 10.1128/jb.175.1.53-63.1993.
When deprived of a carbon source, Escherichia coli induces the synthesis of a group of carbon starvation proteins. The degradation of proteins labeled during starvation was found to be an energy-dependent process which was inhibited by the addition of KCN and accelerated when cells were resupplied with a carbon source. The degradation of the starvation proteins did not require the ATP-dependent Lon protease or the energy-independent proteases protease I, protease IV, OmpT, and DegP. During starvation, mutants lacking either the ClpA or ClpP subunit of the ATP-dependent Clp protease showed a partial reduction in the degradation of starvation proteins. Strains lacking ClpP failed to increase degradation of starvation proteins when glucose was added to starving cells. The clpP mutants showed a competitive disadvantage compared with wild-type cells when exposed to repeated cycles of carbon starvation and growth. Surprisingly, the glucose-stimulated, ClpP-dependent degradation of starvation proteins did not require either the ClpA or ClpB protein. The patterns of synthesis of starvation proteins were similar in clpP+ and clpP cells. The clpP mutants had reduced rates of degradation of certain starvation proteins in the membrane fraction when a carbon source was resupplied to the starved cells.
当缺乏碳源时，大肠杆菌会诱导合成一组碳饥饿蛋白。研究发现，饥饿期间标记的蛋白质降解是一个能量依赖过程，添加氰化钾可抑制该过程，而当细胞重新获得碳源时降解会加速。饥饿蛋白的降解不需要依赖ATP的Lon蛋白酶或不依赖能量的蛋白酶（蛋白酶I、蛋白酶IV、OmpT和DegP）。在饥饿期间，缺乏依赖ATP的Clp蛋白酶的ClpA或ClpP亚基的突变体在饥饿蛋白降解方面表现出部分降低。当向饥饿细胞中添加葡萄糖时，缺乏ClpP的菌株无法增加饥饿蛋白的降解。与野生型细胞相比，clpP突变体在经历反复的碳饥饿和生长循环时表现出竞争劣势。令人惊讶的是，葡萄糖刺激的、依赖ClpP的饥饿蛋白降解不需要ClpA或ClpB蛋白。clpP+和clpP细胞中饥饿蛋白的合成模式相似。当向饥饿细胞重新提供碳源时，clpP突变体中膜组分中某些饥饿蛋白的降解速率降低。
