The central domain of glutamate synthase connects the amino terminal amidotransferase domain with the FMN-binding domain and has an alpha / beta overall topology [1]. This domain appears to be a rudimentary form of the FMN-binding TIM barrel according to SCOP.

1: Structural studies on the synchronization of catalytic centers in glutamate synthase. van den Heuvel RH, Ferrari D, Bossi RT, Ravasio S, Curti B, Vanoni MA, Florencio FJ, Mattevi A; J Biol Chem 2002;277:24579-24583. PMID:11967268