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

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 interactionsFLU, CHL27, PORB, PORC and CHLPphysically interact by blue native page (View interaction)FLUphysically interacts with CHL27, PORB, PORC, CHLP and GluTR by anti tag co-immunoprecipitation (View interaction)FLUphysically interacts with CHL27 by anti bait co-immunoprecipitation (View Interaction: 1, 2)FLUphysically interacts with CHL27 by anti tag co-immunoprecipitation (View interaction)FLUphysically interacts with CHL27, PORB, PORC and CHLP by anti tag co-immunoprecipitation (View interaction)

► FLU is part of a protein complex bound to chloroplast membranes, primarily on the thylakoids.
► FLU co-migrates on BNGE with several enzymes of the chlorophyll biosynthesis pathway.
► FLU co-immunoprecipitates with CHL27, POR B, POR C and geranylgeranyl reductase.
► FLU co-immunoprecipitates with GluTR only in the dark.