Self‐association studies of the bifunctional N‐acetylglucosamine‐1‐phosphate uridyltransferase from Escherichia coli

• Published in: Protein science Vol. 20; no. 4; pp. 745 - 752
• Main Authors: Trempe, Jean‐François, Shenker, Solomon, Kozlov, Guennadi, Gehring, Kalle
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-04-2011; Wiley Subscription Services, Inc
• Subjects: AUC; Bacteriology; beta helix; Crystallography, X-Ray; E coli; Enzymes; Escherichia coli - enzymology; Escherichia coli Proteins - chemistry; GlmU; Models, Molecular; Nucleotidyltransferases - chemistry; Protein Structure, Quaternary; Protein Structure, Tertiary; SAXS; Scattering, Small Angle; self‐association
• ISSN: 0961-8368; 1469-896X
• DOI: 10.1002/pro.608

The N‐acetylglucosamine‐1‐phosphate uridyltransferase (GlmU) is a key bifunctional enzyme in the biosynthesis of UDP‐GlcNAc, a precursor in the synthesis of cell wall peptidoglycan. Crystal structures of the enzyme from different bacterial strains showed that the polypeptide forms a trimer through a unique parallel left‐handed beta helix domain. Here, we show that the GlmU enzyme from Escherichia coli forms a hexamer in solution. Sedimentation equilibrium analytical ultracentrifugation demonstrated that the enzyme is in a trimer/hexamer equilibrium. Small‐angle X‐ray scattering studies were performed to determine the structure of the hexameric assembly and showed that two trimers assemble through their N‐terminal domains. The interaction is mediated by a loop that undergoes a large conformational change in the uridyl transferase reaction, a feature that may affect the enzymatic activity of GlmU.