a, b, Cryo-EM density (a) and ribbon diagrams (b) of tetrameric MapSPARTA in complex with guide RNA (red)-target DNA (blue) duplex. The four protomers of MapSPARTA are colored in green, blue, yellow, and pink, respectively. The four protomers in adopt two different conformations, indicated as State I and State II.
c, d, Ribbon diagrams of MapSPARTA in State I (c) and State II (d). TIR is tightly associated with Ago in State I and loosely in State II.
e, Overlaid structures of MapSPARTA in State I and State II, revealing a dramatic 180º rotation in the TIR domain.
f, Ribbon diagram of MID-MID interaction. The region of interest in shown as a red oval.
g, Electrostatically complementary interface between two MID domains.
h, Detailed MID-MID interactions with interfacial residues highlighted in sticks.