Extended Data Fig. 8: The active center of the AT domain shows the bound substrate interactions.

(a) Crossed-eyes stereo figure showing the density for the active site of the AT domain with substrate bound. The α-carboxyl group on the bound substrate is stabilized by a π-anion interaction with the phenyl ring of F709. (b) Rotated ∼90° around the vertical axis and tilted forward from panel (a) shows interactions between the active center of the AT domain and the bound α-carboxy acyl substrate chain attached to S798. Distances between heavy atoms are tabulated in Å. The catalytic base H906 is ideally placed for the reaction at the γO of S798. The ester carbonyl on the substrate, and hence the oxyanion intermediate formed at that oxygen during the catalytic reaction may be stabilized by R823, H906, and S905. The H906 orientation is aligned by hydrogen bonds from the δN-H to the C = O of G959 and of H962.