The degradation of RcsA by ClpYQ(HslUV) protease in Escherichia coli

Abstract In Escherichia coli , RcsA, a positive activator for transcription of cps (capsular polysaccharide synthesis) genes, is degraded by the Lon protease. In lon mutant, the accumulation of RcsA leads to overexpression of capsular polysaccharide. In a previous study, overproduction of ClpYQ(HslUV) protease represses the expression of cpsB ∷ lacZ , but there has been no direct observation demonstrating that ClpYQ degrades RcsA. By means of a MBP-RcsA fusion protein, we showed that RcsA activated cpsB ∷ lacZ expression and could be rapidly degraded by Lon protease in SG22622 ( lon + ). Subsequently, the comparative half-life experiments performed in the bacterial strains SG22623 ( lon ) and AC3112 ( lon clpY clpQ ) indicated that the RcsA turnover rate in AC3112 was relatively slow and RcsA was stable at 30 °C or 41 °C. In addition, ClpY could interact with RscA in an in vitro pull-down assay, and the more rapid degradation of RcsA was observed in the presence of ClpYQ protease at 41 °C. Thus, we conclude that RcsA is indeed proteolized by ClpYQ protease.