FIG 5.

Asparagine at position 125 is essential for the full activity of LST. (A) An LST saturation mutagenesis library at position 125 was screened by plate halo assay, and all functional clones were picked for further analysis. (B) SDS-PAGE analysis of LST secreted from the halo-forming colonies. Lanes: M, protein marker (top to bottom, 250, 150, 100, 75, 50, 37, 25, and 20 kDa); 1st to 4th, LST secreted from the halo-forming colonies; 5th, commercial LST purchased from Sigma. (C) Sequence alignment of LST with two related staphylocidal lysins (Ale-1 and LytM) shows that N125 is conserved in all three enzymes. Asterisks indicate positions having one identical residue, colons indicate positions occupied by residues having strongly similar properties, periods indicate positions occupied by residues having weakly similar properties, and gaps indicate positions occupied by dissimilar residues.