Open AccessThe two‐component lysis system of Staphylococcus aureus bacteriophage Twort: a large TTG‐start holin and an associated amidase endolysin
Author(s) -
Loessner Martin J,
Gaeng Susanne,
Wendlinger Günther,
Maier Simon K,
Scherer Siegfried
Publication year - 1998
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1998.tb13008.x
Subject(s) - lysin , peptidoglycan , amidase , biology , peptide sequence , bacteriophage , biochemistry , amino acid , escherichia coli , microbiology and biotechnology , plasmid , gene , enzyme
The lysis genes of the virulent Staphylococcus aureus bacteriophage Twort were cloned and their nucleotide sequences determined. The endolysin gene plyTW encodes a 53.3‐kDa protein, whose catalytic site is located in the amino‐terminal domain. An enzymatically active fragment (N‐terminal 271 amino acids) was overexpressed in Escherichia coli and partially purified. The enzyme rapidly cleaves staphylococcal peptidoglycan, and was shown to act as N ‐acetylmuramoyl‐ l ‐alanine amidase (EC 3.5.1.28). Significant sequence homology to the specific cell wall targeting domain of lysostaphin was observed in a 101‐amino acid C‐terminal overlap. However, we found that the large C‐terminal portion (63%, 295 aa) of PlyTW is not required for staphylolytic activity. Located upstream of and overlapping plyTW by 35 bp in a different reading frame (+1), we identified holTW , which starts with a single TTG triplet. The gene specifies a 185‐amino acid (20.5 kDa) holin protein, which features two potential hydrophobic, antiparallel transmembrane domains, and a highly charged, acidic C‐terminus. HolTW is the largest class II holin described to date. It can substitute for the defective allele in phage λ S amber mutants, both in trans from an expression plasmid, and from within gt11:: holTW . The proposed function is the formation of unspecific membrane lesions to promote access of the endolysin to the bacterial peptidoglycan.