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J. Bacteriol., May 1997, 2845-2851, Vol 179, No. 9
MJ Loessner, SK Maier, H Daubek-Puza, G Wendlinger and S Scherer
The ply genes encoding the endolysin proteins from Bacillus cereus phages
Bastille, TP21, and 12826 were identified, cloned, and sequenced. The
endolysins could be overproduced in Escherichia coli (up to 20% of total
cellular protein), and the recombinant proteins were purified by a two-step
chromatographical procedure. All three enzymes induced rapid and specific
lysis of viable cells of several Bacillus species, with highest activity on
B. cereus and B. thuringiensis. Ply12 and Ply21 were experimentally shown
to be N-acetylmuramoyl-L-alanine amidases (EC 3.5.1.28). No apparent holin
genes were found adjacent to the ply genes. However, Ply21 may be endowed
with a signal peptide which could play a role in timing of cell lysis by
the cytoplasmic phage endolysin. The individual lytic enzymes (PlyBa, 41.1
kDa; Ply21, 29.5 kDa, Ply12, 27.7 kDa) show remarkable heterogeneity, i.e.,
their amino acid sequences reveal only little homology. The N-terminal part
of Ply21 was found to be almost identical to the catalytic domains of a
Bacillus sp. cell wall hydrolase (CwlSP) and an autolysin of B. subtilis
(CwlA). The C terminus of PlyBa contains a 77-amino-acid sequence repeat
which is also homologous to the binding domain of CwlSP. Ply12 shows
homology to the major autolysins from B. subtilis and E. coli. Comparison
with database sequences indicated a modular organization of the phage lysis
proteins where the enzymatic activity is located in the N-terminal region
and the C-termini are responsible for specific recognition and binding of
Bacillus peptidoglycan. We speculate that the close relationship of the
phage enzymes and cell wall autolysins is based upon horizontal gene
transfer among different Bacillus phages and their hosts.
Copyright © 1997, American Society for Microbiology
Three Bacillus cereus bacteriophage endolysins are unrelated but reveal high homology to cell wall hydrolases from different bacilli
Institut fur Mikrobiologie, Forschungszentrum fur Milch und Lebensmittel Weihenstephan, Technische Universitat Munchen, Freising,Germany. M.J.Loessner@lrz.tu-muenchen.de
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