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Figure 2
Structure of GlgM from M. smegmatis and comparison with bacterial glycogen synthases. (a, b) Orthogonal views of the GlgM homodimer depicted in cartoon representation with the noncrystallographic twofold axis running vertically and into the screen, respectively (black symbol); the left-hand subunit is in rainbow colours from blue at the N-terminus through to red at the C-terminus and the right-hand subunit is shown in grey. (c) Structure of monomeric E. coli glycogen synthase (EcGS; PDB entry 2qzs) depicted to allow comparison with the left-hand GlgM subunit in (b). Also shown, as van der Waals spheres, are the ADP and α-D-glucose (GLC) ligands bound to EcGS. The asterisks indicate the two β-strands that are not present in the central β-sheet of the N-terminal domain in GlgM. (d, e) Conformational differences between open (PDB entry 3d1j) and closed (PDB entry 2qzs) states of EcGS compared with the differences between the two protomers of the GlgM homodimer. In both panels, the structures were superposed on the C-terminal domain and thus emphasize the shift in the N-terminal domain, which is indicated by the two-headed purple arrow; the purple asterisk marks the approximate pivot point. (f) Structure of trimeric P. abyssi glycogen synthase (PaGS; PDB entry 3fro) as viewed down the noncrystallographic threefold axis (black symbol) and displayed on a smaller scale with respect to the other images. (g) Close-up of the conserved GlgM (cream C atoms) and EcGS (grey C atomss; PDB entry 2qzs) donor-binding site displaying a superposition of structurally equivalent key residues (labels refer to GlgM only; see the main text for E. coli numbering). Also shown are the ADP and α-D-glucose (GLC) ligands (green C atoms) bound to EcGS. The figures were prepared using CCP4mg (McNicholas et al., 2011 ![]() |