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Asymmetric cryo-EM reconstruction of E. coli DegQ 12-mer in complex with lysozyme
Structural highlights
FunctionDEGQ_ECOLI DegQ could degrade transiently denatured and unfolded proteins which accumulate in the periplasm following stress conditions. DegQ is efficient with Val-Xaa and Ile-Xaa peptide bonds, suggesting a preference for a beta-branched side chain amino acids. Only unfolded proteins devoid of disulfide bonds appear capable to be cleaved, thereby preventing non-specific proteolysis of folded proteins. DegQ can substitute for the periplasmic protease DegP.[1] [2] Publication Abstract from PubMedThe HtrA protein family combines chaperone and protease activities and is essential for protein quality control in many organisms. Whereas the mechanisms underlying the proteolytic function of HtrA proteins are well characterized, their chaperone activity remains poorly understood. Here we describe cryo-EM structures of Escherichia coli DegQ in its 12- and 24-mer states in complex with model substrates, providing a structural model of HtrA chaperone action. Up to six lysozyme substrates bind inside the DegQ 12-mer cage and are visualized in a close-to-native state. An asymmetric reconstruction reveals the binding of a well-ordered lysozyme to four DegQ protomers. DegQ PDZ domains are located adjacent to substrate density and their presence is required for chaperone activity. The substrate-interacting regions appear conserved in 12- and 24-mer cages, suggesting a common mechanism of chaperone function. Newly folded substrates inside the molecular cage of the HtrA chaperone DegQ.,Malet H, Canellas F, Sawa J, Yan J, Thalassinos K, Ehrmann M, Clausen T, Saibil HR Nat Struct Mol Biol. 2012 Jan 15;19(2):152-7. doi: 10.1038/nsmb.2210. PMID:22245966[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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