Catalyzes the reductive conversion of 2-oxoglutarate plus glutamine to two molecules of glutamate, using reduced ferredoxin as the electron donor (PubMed:9507092). Contains one FMN but no FAD (PubMed:8651698). The FMN-binding domain is also involved in the delivery of sulfite to the reaction center of SQD1 (PubMed:15752726). 2 L-glutamate + 2 oxidized [2Fe-2S]-[ferredoxin] = 2-oxoglutarate + 2 H(+) + L-glutamine + 2 reduced [2Fe-2S]-[ferredoxin] Binds 1 [3Fe-4S] cluster. Inhibited by N-bromosuccinimide, which is specific for modification of tryptophan residues probably involved in the electron transfer from ferredoxin. Amino-acid biosynthesis; L-glutamate biosynthesis via GLT pathway; L-glutamate from 2-oxoglutarate and L-glutamine (ferredoxin route): step 1/1. Energy metabolism; nitrogen metabolism. Interacts with ferredoxin (PubMed:1910284). Interacts (via FMN-binding domain) with SQD1 (PubMed:15752726). Expressed in young leaves. Not detected in mature leaves. Belongs to the glutamate synthase family.