Fig. 15.

A) Sequence alignment of ER types by stereochemical outcome. The diagnostic tyrosine and valine are indicated in yellow. Other residues that correlate with stereochemical outcome but do not appear to have any impact in mutagenesis studies are indicated in yellow. The alignment was performed with MUSCLE. B) Homology model of EryER4 indicating a hypothesis for the role of the diagnostic tyrosine, which provides steric crowding and prevents approach from the re face. C) Homology model of RapER13 indicating a hypothesis for the role of the diagnostic valine, which sterically affords space for reduction from the re face. Panels B–C reproduced with permission from ref. [129], [131].