The enzyme backbones are drawn with solid ribbons, the catalytic histidines are shown with scaled balls and sticks. (A) Fab A (PDB#1MKA), the dehydratase–isomerase, in green with the active site volume indicated by a faint pink cloud. (B)
P. aeruginosa Fab Z (PDB#1U1Z), the standard dehydratase, in orange with the active site volume indicated by a faint blue cloud. Note the shorter binding tunnel in FabA and the slight difference in the angle of the two tunnels (indicated with dashed lines), hypothesized to allow for C-3 cis double bond formation in FabA.