Analysis of crystalline and solution states of ligand-free spermidine N-acetyltransferase (SpeG) from Escherichia coli

• Published in: Acta crystallographica. Section D, Biological crystallography. Vol. 75; no. Pt 6; pp. 545 - 553
• Main Authors: Filippova, Ekaterina V, Weigand, Steven, Kiryukhina, Olga, Wolfe, Alan J, Anderson, Wayne F
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.06.2019
• Subjects: Acetylation; Acetyltransferase; Acetyltransferases - chemistry; Bacteria; Coenzyme A; Crystal structure; Crystallization; Crystallography, X-Ray - methods; E coli; Escherichia coli; Escherichia coli K12 - enzymology; Escherichia coli Proteins - chemistry; Ligands; Models, Molecular; Oligomers; Organic chemistry; Pathogens; Protein structure; Protein Structure, Quaternary; Spermidine; Toxicity; Vibrio; SpeG; GNAT family; spermidine N-acetyltransferase; Escherichia coli; polyamine acetylation
• ISSN: 0907-4449; 2059-7983; 1399-0047
• DOI: 10.1107/S2059798319006545

Spermidine N-acetyltransferase (SpeG) transfers an acetyl group from acetyl-coenzyme A to an N-terminal amino group of intracellular spermidine. This acetylation inactivates spermidine, reducing the polyamine toxicity that tends to occur under certain chemical and physical stresses. The structure of the SpeG protein from Vibrio cholerae has been characterized: while the monomer possesses a structural fold similar to those of other Gcn5-related N-acetyltransferase superfamily members, its dodecameric structure remains exceptional. In this paper, structural analyses of SpeG isolated from Escherichia coli are described. Like V. cholerae SpeG, E. coli SpeG forms dodecamers, as revealed by two crystal structures of the ligand-free E. coli SpeG dodecamer determined at 1.75 and 2.9 Å resolution. Although both V. cholerae SpeG and E. coli SpeG can adopt an asymmetric open dodecameric state, solution analysis showed that the oligomeric composition of ligand-free E. coli SpeG differs from that of ligand-free V. cholerae SpeG. Based on these data, it is proposed that the equilibrium balance of SpeG oligomers in the absence of ligands differs from one species to another and thus might be important for SpeG function.