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

CHRISTIAN TROETSCHEL; ALBAUM, STEFAN; MICAELA CERLETTI; FERRARI, MARÍA CELESTE; ANSGAR POETSCH; ROBERTO PAGGI; GUEVARA, CARINA RAMALLO; ROSANA DE CASTRO

JOURNAL OF PROTEOME RESEARCH

AMER CHEMICAL SOC

Lugar: Washington; Año: 2018 vol. 17 p. 1158 - 1171

1535-3893

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. In this study 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 absence of Lon and increased degradation in 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.