title: Structural Basis for the Magnesium-Dependent Activation and Hexamerization of the Lon AAA+ Protease.
abstract: The Lon AAA+ protease (LonA) plays important roles in protein homeostasis and regulation of diverse biological processes. LonA behaves as a homomeric hexamer in the presence of magnesium (Mg(2+)) and performs ATP-dependent proteolysis. However, it is also found that LonA can carry out Mg(2+)-dependent degradation of unfolded protein substrate in an ATP-independent manner. Here we show that in the presence of Mg(2+) LonA forms a non-secluded hexameric barrel with prominent openings, which explains why Mg(2+)-activated LonA can operate as a diffusion-based chambered protease to degrade unstructured protein and peptide substrates efficiently in the absence of ATP. A 1.85 Å crystal structure of Mg(2+)-activated protease domain reveals Mg(2+)-dependent remodeling of a substrate-binding loop and a potential metal-binding site near the Ser-Lys catalytic dyad, supported by biophysical binding assays and molecular dynamics simulations. Together, these findings reveal the specific roles of Mg(2+) in the molecular assembly and activation of LonA.
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan 11529, ROC; Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan 10617, ROC.
authors.forename: Shih-Chieh
authors.initials: SC
authors.lastname: Su
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan 11529, ROC; Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu, Taiwan 30013, ROC.
authors.forename: Chien-Chu
authors.initials: CC
authors.lastname: Lin
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan 11529, ROC.
authors.forename: Hui-Chung
authors.initials: HC
authors.lastname: Tai
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan 11529, ROC.
authors.forename: Mu-Yueh
authors.initials: MY
authors.lastname: Chang
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan 11529, ROC.
authors.forename: Meng-Ru
authors.initials: MR
authors.lastname: Ho
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan 11529, ROC.
authors.forename: C Satheesan
authors.initials: CS
authors.lastname: Babu
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan 11529, ROC.
authors.forename: Jiahn-Haur
authors.initials: JH
authors.lastname: Liao
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan 11529, ROC; Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan 10617, ROC.
authors.forename: Shih-Hsiung
authors.initials: SH
authors.lastname: Wu
authors.affiliation: Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan 11529, ROC.
authors.forename: Yuan-Chih
authors.initials: YC
authors.lastname: Chang
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan 11529, ROC; Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 30013, ROC.
authors.forename: Carmay
authors.initials: C
authors.lastname: Lim
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan 11529, ROC; Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan 10617, ROC. Electronic address: chungi@gate.sinica.edu.tw.
authors.forename: Chung-I
authors.initials: CI
authors.lastname: Chang
mesh_terms: D049069:ATP-Dependent Proteases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D000069286:Bortezomib / Q000494:pharmacology; D008274:Magnesium / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D062105:Molecular Docking Simulation; D011480:Protease Inhibitors / Q000494:pharmacology; D011485:Protein Binding; D055503:Protein Multimerization
chemical_list: D024101:Mitochondrial Proteins; D011480:Protease Inhibitors; D000069286:Bortezomib; D049069:ATP-Dependent Proteases; C000595973:LONP1 protein, human; D008274:Magnesium