Fig. 3. The GMCBM21 domain binds glycogen and recruits substrates.
(A) Overlay of the 2D [1H,15N] TROSY spectrum of [2H,15N]-labeled GM64–237 in the presence (red) and absence (black) of PP1α7–330. GMCBM21 residues that interact with PP1 are labeled. Residues that belong to GM64–93 are highlighted (*). (B) Interacting residues mapped onto the surface of GMCBM21 show that they form a contiguous surface around the β3-β4 loop (pink). (C) Model of the interaction of GMCBM21 and PP1. Residues of GMCBM21 shown to interact with PP1 are depicted as blue sticks. (D) CSP mapping of GMCBM21 bound to α-CD (blue) or β-CD (black) versus residue number (right, GMCBM21 secondary structure). Site 1 and site 2 are labeled and marked with dotted lines. (E) CSPs shown in (D) mapped onto the structure of GMCBM21 and colored by magnitude of the chemical shift difference (Δδ). One, two, and three SDs away from the mean are colored cyan, light blue, and red, respectively. Maltoheptose (G7) has been docked onto the GMCBM21 structure by superimposing GMCBM21 with the crystal structure of the RoGACBM21-G7 complex, highlighting the two sugar binding sites: site 1 (bottom) and site 2 (top).