Proteome turnover analysis identifies phytoene synthase as a Lon protease substrate in Haloferax volcanii

CERLETTI M.; CARINA RAMALLO GUEVARA; DE CASTRO R.E.; PAGGI R.A; ALBAUM S; TROTSCHEL C.; POETSCH A.

Córdoba

Congreso; LII Reunión SAIB 2016; 2016

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

In bacteria and eukaryotes energy-dependent Lon proteases (soluble enzymes, LonA) are involved in protein quality control and in the degradation of specific proteins controlling diverse cellular functions. The archaeal version of Lon (LonB) is unusually membrane-associated and its physiological role and natural substrates remain unknown. We have demonstrated that LonB is an essential protease in the archaeon Haloferax volcanii and suboptimal levels of this enzyme affect growth rate, cell shape, lipid composition and cell pigmentation. In this study we examined the proteome turnover of a H. volcanii conditional LonB mutant under suboptimal (- trp) and physiological (+ trp) protease levels to discover its natural substrates. To this end, heavy isotope metabolic labeling coupled to tandem mass spectrometry was applied. The overall protein synthesis and degradation rates as well as the turnover of several specific proteins showed significant differences (p-value ≤ 0.05) in response to changes in Lon expression. Based on these results we identified several potential LonB substrates including phytoene synthase, an enzyme that controls a rate-limiting step in the carotenoid biosynthesis pathway. This is the first study that examines the proteome turnover in an archaeon as well as the first report of a natural target of the archaeal membrane-bound Lon protease.Supported by CONICET, UNMDP, ANPCyT and MINCyT-BMBF.