Fig. 3: Structural Basis for SETD3-EV71 2A Interactions.

a EV71 2A occupies the central cleft of SETD3, where it makes two discrete contacts with each domain of SETD3, denoted Site-1 and Site-2. b Left and right, details of intermolecular interactions at Site-1 and Site-2. Residues important for intermolecular interactions are shown in stick representation and labeled; hydrogen bonds and salt bridges are shown as dashed lines. c Structure superimposition of unliganded SETD3 (PDB: 3SMT), SETD3 complexed by actin peptide (PDB: 6OX2), and the cryo-EM structure of the SETD3-EV71 2A complex reported in this study. Binding by actin peptide or EV 71 2A induces large conformational changes in the SETD3 SET domain, indicated by arrows. Left insert, magnified view of SETD3 active site, illustrating interaction details between SETD3-Actin peptide and between SETD3-EV71 2A. Right insert, magnified view of EV71 2A protease active site; substrate peptide (magenta) is modeled in the active site by superimposing an EV71 2A-peptide complex (PDB: 4FVD) with the EV71 2A chain in the complex. d The R-strand of SETD3 forms backbone hydrogen bonds with the β-bII1 strand of EV71 2A, where the β-bII1 strand would clash with the bound actin peptide. e The MTase activity of SETD3 is inhibited by EV71 2A. Blue curve, SETD3 alone; red curve, SETD3:EV71 2A molar ratio=1:2; green curve, SETD3:EV71 2A molar ratio = 1:5. Data are mean ± s.d. from three independent experiments (n  =  3). Source data are provided as a Source Data filef BLI experiments illustrating preloading EV71 2A to SETD3 (immobilized on SA biosensor) was barely disrupted by subsequent loading of AP-actin. Black curve, SETD3 loaded biosensor was first exposed to EV71 2A and subsequently AP-actin; Red curve, SETD3 loaded biosensor was first exposed to G buffer and subsequently AP-actin. g BLI experiments illustrating preloading AP-actin to SETD3 (immobilized on SA biosensor) had negligible effect on subsequent binding of EV71 2A. Black curve, SETD3 loaded biosensor was first exposed to AP-actin and subsequently EV71 2A; Red curve, SETD3 loaded biosensor was first exposed to G buffer and subsequently EV71 2A.