Bacterial AcpS. (a) Multiple sequence alignment of some bacterial AcpS enzymes with known X-ray structures: S. aureus (PDB entry 3f09), B. anthracis (PDB entry 3hyk), B. subtilis (PDB entry 1f7l), S. pneumoniae (PDB entry 1fth), V. cholerae (PDB entry 3qmn) and S. coelicolor (PDB entry 2jbz). The conserved residues are shaded red and similar residues are displayed in red letters. Residues of the central β-sheet of AcpSSA numbered in (c) are marked with a plus sign. Asterisks indicate residues of AcpSVC that coordinate CoA/K (see Fig. 3c). The coordinators of two magnesium cations, Mg-I and Mg-II (see Figs. 4d and 4e), are shown as I and II, respectively. The green box indicates the Glu-II position, an alternative glutamate of the group II and III PPTs that is involved in coordination of Mg-I. Multiple sequence alignment was performed by ClustalW (available at http://www.genome.jp/tools/clustalw) and the figure was generated with ESPript2.2 (Gouet et al., 1999). (b) The quaternary structure of the AcpS enzyme (apo-AcpSSA is shown). (c) The tertiary structure of a single polypeptide of AcpSSA. The residues (in green) of the central β-sheet that are exposed to the interior of AcpS trimer are numbered according to the sequence of AcpSSA. (d) Monomer of AcpSVC with the structurally distinct helix α6 in dark blue.