FLU, a negative feedback regulator of tetrapyrrole biosynthesis, is physically linked to the final steps of the Mg⁺⁺‐branch of this pathway

Abstract

Edited by Ulf-Ingo FlüggeKeywords: Protochlorophyllide FLU Glutamyl-tRNA reductase Arabidopsis a b s t r a c t Regulation of tetrapyrrole biosynthesis in higher plants has been attributed to negative feedback control. Two effectors of feedback inhibition have been identified, heme and the FLU protein. Inhibition by heme implicates the Fe-branch via regulation of the initial step of tetrapyrrole synthesis. In the present work a FLU-containing chloroplast membrane complex was identified, that besides FLU comprises the four enzymes catalyzing the final steps of chlorophyll synthesis. The results support the notion that FLU links chlorophyll synthesis and the target of feedback control, glutamyl-tRNA reductase, thereby allowing also the Mg-branch to control the initial step of tetrapyrrole synthesis. Structured summary of protein interactions:FLU, CHL27, PORB, PORC and CHLP physically interact by blue native page (View interaction) FLU physically interacts with CHL27, PORB, PORC, CHLP and GluTR by anti tag co-immunoprecipitation (View interaction) FLU physically interacts with CHL27 by anti bait co-immunoprecipitation (View Interaction: 1, 2) FLU physically interacts with CHL27 by anti tag co-immunoprecipitation (View interaction) FLU physically interacts with CHL27, PORB, PORC and CHLP by anti tag co-immunoprecipitation (View interaction)

LIL3, a Light-Harvesting Complex Protein, Links Terpenoid and Tetrapyrrole Biosynthesis in Arabidopsis thaliana

“…Moreover, a POR-GluTR interaction was found by the same approach. This interaction is consistent with the findings reported by Kauss et al (2012), who proposed the formation of a protein complex consisting of CHL27, POR, FLU, and GluTR in chloroplasts of dark-grown plants. The POR reaction provides Chlide, one of the two substrates of CHLG.…”

Posttranslational Influence of NADPH-Dependent Thioredoxin Reductase C on Enzymes in Tetrapyrrole Synthesis

“…Either CHLH activity contributes to the methyltransferase activity, as proposed by Shepherd et al (2005), or CHLH is needed for the stability of a multienzymatic complex including CHLM. In this context, a protein complex consisting of CHL27, POR, GluTR, and other proteins has been recently reported for the tight repression of ALA synthesis in darkness by the negative regulator FLU in angiosperms (Meskauskiene et al, 2001;Kauss et al, 2012). It remains open whether other proteins of Chl synthesis, including the CHLH subunit and CHLM, are part of this protein complex.…”

“…Two important posttranslational regulators, FLU and Genome Uncoupled4 (GUN4), have been identified that modulate the enzyme activities of glutamyl-tRNA reductase (GluTR) and Mg chelatase, respectively. In response to accumulating PChlide, the FLU protein represses ALA synthesis in darkness by interaction with GluTR1 (Meskauskiene et al, 2001;Richter et al, 2010;Kauss et al, 2012), which is one of the two analyzed isoforms. GUN4 has been identified in a mutant screen for modifications of retrograde signaling between chloroplasts and the nucleus (Larkin et al, 2003).…”

Phosphorylation of GENOMES UNCOUPLED 4 Alters Stimulation of Mg Chelatase Activity in Angiosperms

“…S3C). In dark, the flow of intermediates is rapidly attenuated by the FLU-protochlorophyllide-dependent repression of GluTR activity (Meskauskiene et al, 2001;Meskauskiene and Apel, 2002;Lee et al, 2003;Richter et al, 2010;Kauss et al, 2012). By inhibition of ALA synthesis, the rate-limiting step of TBS, the steady-state levels of MgP and MgPMME, were below the detection limit and protochlorophyllide is the only porphyrin, which accumulates in dark due to the light dependency of protochlorophyllide oxidoreductase (POR).…”