Structural Insight Into How Streptomyces Coelicolor Maltosyl Transferase Glge Binds Alpha-Maltose 1-Phosphate and Forms a Maltosyl-Enzyme Intermediate.Syson, K., Stevenson, C.E.M., Rashid, A.M., Saalbach, G., Tang, M., Tuukkanen, A., Svergun, D.I., Withers, S.G., Lawson, D.M., Bornemann, S.
(2014) Biochemistry 53: 2494
- PubMed: 24689960
- DOI: 10.1021/bi500183c
- Primary Citation of Related Structures:
- PubMed Abstract:
GlgE (EC 188.8.131.52) is an α-maltose 1-phosphate:(1→4)-α-d-glucan 4-α-d-maltosyltransferase of the CAZy glycoside hydrolase 13_3 family. It is the defining enzyme of a bacterial α-glucan biosynthetic pathway and is a genetically validated anti-tubercu ...
GlgE (EC 184.108.40.206) is an α-maltose 1-phosphate:(1→4)-α-d-glucan 4-α-d-maltosyltransferase of the CAZy glycoside hydrolase 13_3 family. It is the defining enzyme of a bacterial α-glucan biosynthetic pathway and is a genetically validated anti-tuberculosis target. It catalyzes the α-retaining transfer of maltosyl units from α-maltose 1-phosphate to maltooligosaccharides and is predicted to use a double-displacement mechanism. Evidence of this mechanism was obtained using a combination of site-directed mutagenesis of Streptomyces coelicolor GlgE isoform I, substrate analogues, protein crystallography, and mass spectrometry. The X-ray structures of α-maltose 1-phosphate bound to a D394A mutein and a β-2-deoxy-2-fluoromaltosyl-enzyme intermediate with a E423A mutein were determined. There are few examples of CAZy glycoside hydrolase family 13 members that have had their glycosyl-enzyme intermediate structures determined, and none before now have been obtained with a 2-deoxy-2-fluoro substrate analogue. The covalent modification of Asp394 was confirmed using mass spectrometry. A similar modification of wild-type GlgE proteins from S. coelicolor and Mycobacterium tuberculosis was also observed. Small-angle X-ray scattering of the M. tuberculosis enzyme revealed a homodimeric assembly similar to that of the S. coelicolor enzyme but with slightly differently oriented monomers. The deeper understanding of the structure-function relationships of S. coelicolor GlgE will aid the development of inhibitors of the M. tuberculosis enzyme.
Department of Biological Chemistry, John Innes Centre, Norwich Research Park , Norwich NR4 7UH, United Kingdom.