The escherichia coli ClpYQ protease recognizes the C-terminal tail of SulA

The Escherichia coli ATP dependent proteases play several important roles in protein quality control and they use the energy from ATP hydrolysis to recognize and degrade the abnormal proteins. ClpYQ protease, one of the ATP dependent proteases, is a two component complex. ClpY recognizes, unfolds and translocates the natural substrates into the catalytic core site of ClpQ for the degradation. The cell division inhibitor, SulA, induced during an SOS response, prevented a cell division. However, both Lon and ClpYQ proteases were capable of degrading it and that could restore the normal cell growth. In this study, through the in vitro assays, the 141 to 150 residues of SulA were shown necessary for interaction with ClpY. There is a conserved region between 142 to 147 residues, G¹⁴²F¹⁴³I, ⁴⁴M¹⁴⁵R¹⁴⁶P¹⁴⁷, in SulA, from Gram-negative bacteria. SulA^∗ I144N point mutant, with a substitution of Asn for Ile, was further used for detection of its degradation with ClpYQ protease. MBP(maltose-binding-protein)-SulA^∗I144N has a longer half-life than that of MBP-SulA in the presence of ClpQ and ClpY. Moreover, SulA^∗I144N mutant has no inhibitory activity on cell division; this mutant has an effect on the function of SulA. Our results suggested that the conserved hydrophobic region in SulA is necessary for its inhibitory activity as well as for an association with ClpY for its degradation by ClpYQ protease.