Tryggvesson Anders, Ståhlberg Frida M, Töpel Mats, Tanabe Noriaki, Mogk Axel, Clarke Adrian K
Department of Biological and Environmental Sciences, Gothenburg University, Box 461, 405 30 Gothenburg, Sweden.
Department of Applied Biosciences, Kinki University, Nakamachi 3327-204, Nara, Japan.
FEBS Lett. 2015 Dec 21;589(24 Pt B):4039-46. doi: 10.1016/j.febslet.2015.11.026. Epub 2015 Nov 24.
The adaptor protein ClpS associates to the Clp protease and promotes degradation of N-end rule substrates in eubacteria and in algal/plant chloroplasts. Cyanobacteria are unusual in having two distinct ClpS paralogs. Although ClpSl is typical of bacterial ClpS, ClpS2 differs in crucial ways. ClpS2 in Synechococcus elongatus is a relatively low-abundant, soluble protein essential for phototrophic growth. Like ClpSl, ClpS2 binds to the ClpCP3/R protease to block α-casein degradation and promote that of N-end rule substrates in vitro. However, their substrate specificity differs, with ClpSl recognizing destabilizing Phe and Tyr residues at the substrate N-terminus whereas ClpS2 recognizes Leu. Overall, ClpS2 appears to have independently evolved in cyanobacteria to degrade a particular group of proteins, whose turnover is vital for cell viability.
衔接蛋白ClpS与Clp蛋白酶结合，并促进真细菌以及藻类/植物叶绿体中N端规则底物的降解。蓝细菌的独特之处在于有两个不同的ClpS旁系同源物。虽然ClpS1是典型的细菌ClpS，但ClpS2在关键方面有所不同。聚球藻中的ClpS2是一种相对低丰度的可溶性蛋白，是光合营养生长所必需的。与ClpS1一样，ClpS2在体外与ClpCP3/R蛋白酶结合，以阻断α-酪蛋白的降解并促进N端规则底物的降解。然而，它们的底物特异性不同，ClpS1识别底物N端的不稳定苯丙氨酸和酪氨酸残基，而ClpS2识别亮氨酸。总体而言，ClpS2似乎是在蓝细菌中独立进化而来，以降解特定的一组蛋白质，这些蛋白质的周转对细胞活力至关重要。
