Figure 2 - full size

 

Figure 2.
Fig. 2. Structure of yeast ACP bound to the KS catalytic cleft. (A) The prosthetic PPT group (spheres) covalently attached to the ACP core (cyan) adopts an extended conformation in the fungal FAS complex. The ACP core forms a compact domain with an additional four-helix bundle (gray), rendering fungal ACP considerably larger than the bacterial counterpart (blue, shown in the same orientation). During interdomain substrate shuttling, the PTT arm might fold back on ACP (arrow), thereby inserting the acyl chain into a cavity formed by the ACP core, as observed in the isolated E. coli ACP structure (16). (B) Detailed view of PPT bound in the catalytic cleft of KS. The unbiased threefold averaged F[obs] – F[calc] simulated annealing omit map (green) shows ACP and the phosphate and pantoic acid (PA) moieties of the PPT prosthetic group. Modeling of the additional PPT part shows that the catalytic residues of KS can easily be reached. KS1 and KS2 form the dimer to which ACP is bound.

The above figure is reprinted by permission from the AAAs: Science (2007, 316, 288-290) copyright 2007.