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J Proteome Res. 2018 Mar 2;17(3):1158-1171. doi: 10.1021/acs.jproteome.7b00809. Epub 2018 Feb 15.

LonB Protease Is a Novel Regulator of Carotenogenesis Controlling Degradation of Phytoene Synthase in Haloferax volcanii.

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Instituto de Investigaciones Biológicas, Universidad Nacional de Mar del Plata (UNMDP), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) , Funes 3250 4to nivel, Mar del Plata 7600, Argentina.
Plant Biochemistry, Ruhr University Bochum , 44801 Bochum, Germany.
Bioinformatics Resource Facility, Center for Biotechnology (CeBiTec), Bielefeld University , 33615 Bielefeld, Germany.
School of Biomedical and Healthcare Sciences, Plymouth University , Plymouth PL4 8AA, United Kingdom.


The membrane protease LonB is an essential protein in the archaeon Haloferax volcanii and globally impacts its physiology. However, natural substrates of the archaeal Lon protease have not been identified. The whole proteome turnover was examined in a H. volcanii LonB mutant under reduced and physiological protease levels. LC-MS/MS combined with stable isotope labeling was applied for the identification/quantitation of membrane and cytoplasm proteins. Differential synthesis and degradation rates were evidenced for 414 proteins in response to Lon expression. A total of 58 proteins involved in diverse cellular processes showed a degradation pattern (none/very little degradation in the absence of Lon and increased degradation in the presence of Lon) consistent with a LonB substrate, which was further substantiated for several of these candidates by pull-down assays. The most notable was phytoene synthase (PSY), the rate-limiting enzyme in carotenoid biosynthesis. The rapid degradation of PSY upon LonB induction in addition to the remarkable stabilization of this protein and hyperpigmentation phenotype in the Lon mutant strongly suggest that PSY is a LonB substrate. This work identifies for the first time candidate targets of the archaeal Lon protease and establishes proteolysis by Lon as a novel post-translational regulatory mechanism of carotenogenesis.


Archaea; Haloferax volcanii; LonB substrates; membrane protease; phytoene synthase; proteome turnover

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