Structural highlights
Publication Abstract from PubMedPolyamines are important regulators in all living organisms and are implicated in essential biological processes including cell growth, differentiation and apoptosis. Pseudomonas aeruginosa possesses an spuABCDEFGHI gene cluster that is involved in the metabolism and uptake of two polyamines: spermidine and putrescine. In the proposed gamma-glutamylation-putrescine metabolism pathway, SpuA hydrolyzes gamma-glutamyl-gamma-aminobutyrate (gamma-Glu-GABA) to glutamate and gamma-aminobutyric acid (GABA). In this study, crystal structures of P. aeruginosa SpuA are reported, confirming it to be a member of the class I glutamine amidotransferase (GAT) family. Activity and substrate-binding assays confirm that SpuA exhibits a preference for gamma-Glu-GABA as a substrate. Structures of an inactive H221N mutant were determined with bound glutamate thioester intermediate or glutamate product, thus delineating the active site and substrate-binding pocket and elucidating the catalytic mechanism. The crystal structure of another bacterial member of the class I GAT family from Mycolicibacterium smegmatis (MsGATase) in complex with glutamine was determined for comparison and reveals a binding site for glutamine. Activity assays confirm that MsGATase has activity for glutamine as a substrate but not for gamma-Glu-GABA. The work reported here provides a starting point for further investigation of polyamine metabolism in P. aeruginosa. Structure and mechanism of the gamma-glutamyl-gamma-aminobutyrate hydrolase SpuA from Pseudomonas aeruginosa.,Chen Y, Jia H, Zhang J, Liang Y, Liu R, Zhang Q, Bartlam M Acta Crystallogr D Struct Biol. 2021 Oct 1;77(Pt 10):1305-1316. doi:, 10.1107/S2059798321008986. Epub 2021 Sep 22. PMID:34605433[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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