Structural comparison of bacterial AcpS. (a) Surface diagram of the sequence-based structural alignment of the bacterial AcpS enzymes presented in Fig. 1(a). The structure of apo-AcpSSA is used to display the conservation of the residues, which are colored from blue (variable) to red (100% conserved). The positions of two 3′,5′-ADP molecules (black) in AcpSBA and of CoA (white) in AcpSVC are shown. (b) Stereogram of the monomer–monomer interaction interface in the AcpSSA trimer. Residues are colored from blue (variable) to red (100% conserved). The third molecule is omitted for clarity. (c) Stereogram of the least-squares superposition of the AcpSSA (red), AcpSVC (blue) and AcpSBA (green) structures.