Tracing the active center of Pst using point mutants.
A, sequence and structural alignment of the activity domain of Pst and T4 lysozyme. In the sequence alignment (lines 1–3), the identical residues are marked with asterisk, strongly conserved residues are marked with colon, and weakly conserved residues are marked with period. In the structural alignment, only the identical positions (within a root mean square deviation of 3.5 Å between Cα positions) are marked (*). Residues mutated in Pst for activity assays are marked in green. Active site residues in T4 lysozyme are highlighted in red. B, superposition of the structures of PstA and T4 lysozyme (PDB code 168L) in ribbon representation in two orientations (left and right). Residues chosen for mutagenesis according to the structure and sequence alignment were mutated into alanines (see also A). These residues are marked as sticks together with residue and number for Pst and compared with identical T4 lysozyme positions (T4 lysozyme/Pst). Additional residues mutated in Pst are marked by sticks and residue numbers (Asp-207, Gln-301, and Asp-338).