Catalyzes the NADPH-dependent reduction of glutamyl-tRNA(Glu) to glutamate 1-semialdehyde (GSA). Probably involved in the tetrapyrrole synthesis required for the chlorophyll biosynthesis. (S)-4-amino-5-oxopentanoate + NADP(+) + tRNA(Glu) = H(+) + L-glutamyl-tRNA(Glu) + NADPH Negatively regulated by FLU and heme. Porphyrin-containing compound metabolism; chlorophyll biosynthesis. Porphyrin-containing compound metabolism; protoporphyrin-IX biosynthesis; 5-aminolevulinate from L-glutamyl-tRNA(Glu): step 1/2. Part of the FLU-containing chloroplast membrane complex composed of FLU, CRD1, PORB, PORC, CHLP and HEMA1. Interacts (via C-terminus) with FLU, only in the absence of light. Interacts with GLUTRBP and forms a heterotetramer of two GLUTRBP and two HEMA1 subunits. Interacts with CLPF (PubMed:26419670). Strongly expressed in photosynthetic tissues. Detected in all tissues tested. Circadian-regulation. Up-regulated by light. The N-terminus (65-92) is required for heme inhibition, but not for activity. During catalysis, the active site Cys acts as a nucleophile attacking the alpha-carbonyl group of tRNA-bound glutamate with the formation of a thioester intermediate between enzyme and glutamate, and the concomitant release of tRNA(Glu). The thioester intermediate is finally reduced by direct hydride transfer from NADPH, to form the product GSA (By similarity). Belongs to the glutamyl-tRNA reductase family.