The structure of PA5508 from Pseudomonas aeruginosa, a glutamine synthase (GS) homolog, has been solved at 2.5 Å. Surprisingly, PA5508 forms single hexameric rings rather than the stacked double rings that are characteristic of GS. The C-terminal helical thong motif that links GS rings is present in PA5508; however, it is folded back toward the core of its own polypeptide preventing it from interacting with a second ring. Other unique aspects of the structure illustrate how the enzyme is able to catalyze reactions involving bulky amines rather than ammonia. PA5508 displays no GS activity but instead acts on a variety of linear, cyclic, and aromatic mono- and polyamines.
Pub Type: Journals
glutamine synthase homolog, polyamine, Pseudomonas