Kim Y I, Levchenko I, Fraczkowska K, Woodruff R V, Sauer R T, Baker T A
Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
Nat Struct Biol. 2001 Mar;8(3):230-3. doi: 10.1038/84967.
The Clp/Hsp100 ATPases are hexameric protein machines that catalyze the unfolding, disassembly and disaggregation of specific protein substrates in bacteria, plants and animals. Many family members also interact with peptidases to form ATP-dependent proteases. In Escherichia coli, for instance, the ClpXP protease is assembled from the ClpX ATPase and the ClpP peptidase. Here, we have used multiple sequence alignments to identify a tripeptide 'IGF' in E. coli ClpX that is essential for ClpP recognition. Mutations in this IGF sequence, which appears to be part of a surface loop, disrupt ClpXP complex formation and prevent protease function but have no effect on other ClpX activities. Homologous tripeptides are found only in a subset of Clp/Hsp100 ATPases and are a good predictor of family members that have a ClpP partner. Mapping of the IGF loop onto a homolog of known structure suggests a model for ClpX-ClpP docking.
Clp/Hsp100 ATP酶是六聚体蛋白机器，可催化细菌、植物和动物中特定蛋白质底物的解折叠、拆卸和去聚集。许多家族成员还与肽酶相互作用形成ATP依赖性蛋白酶。例如，在大肠杆菌中，ClpXP蛋白酶由ClpX ATP酶和ClpP肽酶组装而成。在这里，我们使用多序列比对在大肠杆菌ClpX中鉴定出一个对ClpP识别至关重要的三肽“IGF”。该IGF序列似乎是表面环的一部分，其突变会破坏ClpXP复合物的形成并阻止蛋白酶功能，但对其他ClpX活性没有影响。同源三肽仅在Clp/Hsp100 ATP酶的一个子集中发现，并且是具有ClpP伴侣的家族成员的良好预测指标。将IGF环映射到已知结构的同源物上，提出了一个ClpX-ClpP对接模型。
