Single-amino-acid replacements introduced in the N-terminal region of the lysis protein. (A) Scheme of the cytoplasmic, transmembrane, and periplasmic domains of the lysis protein E. All substitutions were introduced in the periplasmic domain. (B) Nucleotide sequence of the region studied, showing the two overlapping reading frames (top, gene D; bottom, gene E) and the amino acid changes introduced.