Fig. 5: The synthase macrocomplex in limiting c-di-GMP.

a Locally refined cryo-EM map and fitted structure of the crownless synthase macrocomplex featuring a c-di-GMP-free synthase in two different views. IM inner membrane. b Cartoon representation of the same assembly. c The cryo-EM map and model of a locally refined BcsRQEF assembly. d A zoom-in on c-di-GMP binding by a composite, dual I-site pocket in closed BcsE. e REC* domain dimerization interface in the non-saturated macrocomplex. f A zoom-in on the BcsA:BcsR interface and summary of the synthase’s interactions with the cytosolic vestibule partners57. g Overall core synthase fold showing unstructured gating loop and an accessible active site.