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Molecular adaptation of the DegQ protease to exert protein quality control in the bacterial cell envelope

Sawa, Justyna, Malet, Helene, Krojer, Tobias, Canellas, Flavia, Ehrmann, Michael and Clausen, Tim 2011. Molecular adaptation of the DegQ protease to exert protein quality control in the bacterial cell envelope. Journal of Biological Chemistry 286 (35) , pp. 30680-30690. 10.1074/jbc.M111.243832

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To react to distinct stress situations and to prevent the accumulation of misfolded proteins, all cells employ a number of proteases and chaperones, which together set up an efficient protein quality control system. The functionality of proteins in the cell envelope of Escherichia coli is monitored by the HtrA proteases DegS, DegP, and DegQ. In contrast with DegP and DegS, the structure and function of DegQ has not been addressed in detail. Here, we show that substrate binding triggers the conversion of the resting DegQ hexamer into catalytically active 12- and 24-mers. Interestingly, substrate-induced oligomer reassembly and protease activation depends on the first PDZ domain but not on the second. Therefore, the regulatory mechanism originally identified in DegP should be a common feature of HtrA proteases, most of which encompass only a single PDZ domain. Using a DegQ mutant lacking the second PDZ domain, we determined the high resolution crystal structure of a dodecameric HtrA complex. The nearly identical domain orientation of protease and PDZ domains within 12- and 24-meric HtrA complexes reveals a conserved PDZ1 → L3 → LD/L1/L2 signaling cascade, in which loop L3 senses the repositioned PDZ1 domain of higher order, substrate-engaged particles and activates protease function. Furthermore, our in vitro and in vivo data imply a pH-related function of DegQ in the bacterial cell envelope.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Biosciences
Subjects: Q Science > QP Physiology
Uncontrolled Keywords: Allosteric Regulation; Crystal Structure; Enzyme Mechanisms; Protein Degradation; Serine Protease; Bacterial Cell Envelope; HtrA; Protein Quality Control
Publisher: American Society for Biochemistry and Molecular Biology
ISSN: 0021-9258
Last Modified: 04 Jun 2017 06:10

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