Proteolysis by cytoplasmic, energy-dependent proteases plays a critical role in many regulatory circuits, keeping basal levels of regulatory proteins low and rapidly removing proteins when they are no longer needed. In bacteria, four families of energy-dependent proteases carry out degradation. In all of them, substrates are first recognized and bound by ATPase domains and then unfolded and translocated to a sequestered proteolytic chamber. Substrate selection depends not on ubiquitin but on intrinsic recognition signals within the proteins and, in some cases, on adaptor or effector proteins that participate in delivering the substrate to the protease. For some, the activity of these adaptors can be regulated, which results in regulated proteolysis. Recognition motifs for proteolysis are frequently found at the N and C termini of substrates. Proteolytic switches appear to be critical for cell cycle development in Caulobacter crescentus, for proper sporulation in Bacillus subtilis, and for the transition in and out of stationary phase in Escherichia coli. In eukaryotes, the same proteases are found in organelles, where they also play important roles.

中文翻译：

---

细菌调节回路中的蛋白水解。

细胞质能量依赖型蛋白酶的蛋白水解作用在许多调节回路中都起着至关重要的作用，可将调节蛋白的基础水平保持在较低水平，并在不再需要时迅速去除蛋白。在细菌中，能量依赖的蛋白酶的四个家族进行降解。在所有这些底物中，底物首先被ATPase域识别并结合，然后展开并易位到隔离的蛋白水解室中。底物的选择不取决于泛素，而是取决于蛋白质内的内在识别信号，在某些情况下，还取决于参与将底物递送至蛋白酶的衔接子或效应蛋白。对于某些人来说，这些衔接子的活性可以被调节，这导致被调节的蛋白水解。经常在底物的N和C末端发现蛋白水解的识别基序。蛋白水解开关对于新月形杆菌的细胞周期发展，枯草芽孢杆菌中的适当孢子形成以及大肠杆菌中固定相的进出过渡至关重要。在真核生物中，在细胞器中发现了相同的蛋白酶，它们在其中也起着重要的作用。