PMID: 26037924 , Related PDB ids: 3RO3, 4N7R, 4YVO, 4YVQ

Authors:

Zhang M, Zhang F, Fang Y, Chen X, Chen Y, Zhang W, Dai HE, Lin R, Liu L

Title:

The Non-canonical Tetratricopeptide Repeat (TPR) Domain of Fluorescent (FLU) Mediates Complex Formation with Glutamyl-tRNA Reductase.

Journal:

J Biol Chem. 2015 Jul 10;290(28):17559-65. doi: 10.1074/jbc.M115.662981. Epub, 2015 Jun 2.

Abstract:

The tetratricopeptide repeat (TPR)-containing protein FLU is a negative regulator of chlorophyll biosynthesis in plants. It directly interacts through its TPR domain with glutamyl-tRNA reductase (GluTR), the rate-limiting enzyme in the formation of delta-aminolevulinic acid (ALA). Delineation of how FLU binds to GluTR is important for understanding the molecular basis for FLU-mediated repression of synthesis of ALA, the universal tetrapyrrole precursor. Here, we characterize the FLU-GluTR interaction by solving the crystal structures of the uncomplexed TPR domain of FLU (FLU(TPR)) at 1.45-A resolution and the complex of the dimeric domain of GluTR bound to FLU(TPR) at 2.4-A resolution. Three non-canonical TPR motifs of each FLU(TPR) form a concave surface and clamp the helix bundle in the C-terminal dimeric domain of GluTR. We demonstrate that a 2:2 FLU(TPR)-GluTR complex is the functional unit for FLU-mediated GluTR regulation and suggest that the formation of the FLU-GluTR complex prevents glutamyl-tRNA, the GluTR substrate, from binding with this enzyme. These results also provide insights into the spatial regulation of ALA synthesis by the membrane-located FLU protein.