Fig. 3: The crystal structure of HaPE645.

a Cartoon representation of the closed form HaPE645 structure (αL cyan; αS pale cyan; corresponding β subunits forest and lime green, respectively). b The electron density (orange mesh) for the β82 chromophore attached to the αSβ protomer clearly shows that it is PCB, where pyrrole ring D is part of the conjugated structure. c In contrast, the electron density (orange mesh) for the β82 chromophore attached to the αLβ protomer clearly shows that it is PEB, where pyrrole ring D is separated by two sp3 carbon atoms from the conjugated ring structure. d Shows the interactions between the N-terminus of the αS subunit and the PCB β82 chromophore in HaPE645, which are similar to those seen in e for the PCB β82 chromophore in CsPC645. f Shows the interactions between the N-terminus of the αL subunit and the PEB β82 chromophore in HaPE645, which are similar to those seen in g for the PCB β82 chromophore in HvPC612.