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Publication Abstract from PubMed

The spermidine N-acetyltransferase SpeG is a dodecameric enzyme that catalyzes the transfer of an acetyl group from acetyl-coenzyme A to polyamines such as spermidine and spermine. SpeG has an allosteric polyamine-binding site and acetylating polyamines regulates their intracellular concentrations. The structures of SpeG from Vibrio cholerae in complexes with polyamines and cofactor have been characterized earlier. Here, we present the dodecameric structure of SpeG from V. cholerae in a ligand-free form in three different conformational states: open, intermediate and closed. All structures were crystallized in C2 space group symmetry and contain 6 monomers in the asymmetric unit cell. Two hexamers related by crystallographic twofold symmetry form the SpeG dodecamer. The open and intermediate states have a unique open dodecameric ring. This SpeG dodecamer is asymmetric except for the one twofold axis and is unlike any known dodecameric structure. Using a fluorescence thermal shift assay, size exclusion chromatography with multi-angle light scattering, small angle X-ray scattering analysis, negative stain electron microscopy, and structural analysis we demonstrate that this unique open dodecameric state exists in solution. Our combined results indicate that polyamines trigger conformational changes and induce the symmetric closed dodecameric state of the protein when they bind to their allosteric sites.

Substrate induced allosteric change in the quaternary structure of the spermidine N-acetyltransferase SpeG.,Filippova EV, Weigand S, Osipiuk J, Kiryukhina O, Joachimiak A, Anderson WF J Mol Biol. 2015 Sep 24. pii: S0022-2836(15)00536-7. doi:, 10.1016/j.jmb.2015.09.013. PMID:26410587^[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.