Modular organization of the lytic enzymes of Streptococcus pneumoniae and its bacteriophages.
The nucleotide sequences of genes cpl7 and cpl9 of the Streptococcus pneumoniae bacteriophages Cp-7 and Cp-9, encoding the muramidases CPL-7 and CPL-9, respectively, have been determined. The N-terminal domains of CPL-7 and CPL-9 were virtually identical to that previously reported for the CPL-1 muramidase. The C-terminal domain of the CPL-7 muramidase, however, was different from those of the host amidase and the phage Cp-1 and Cp-9 lysozymes. Whereas all enzymes studied are characterized by repeated sequences at their C termini, the repeat-unit lengths are 20 amino acids (aa) in CPL-1, CPL-9 and in the host amidase, but 48 aa in CPL-7. Six repeated sequences represent the C-terminal domains of CPL-1, CPL-9 and the host amidase, and 2.8 perfect tandem repetitions that of CPL-7. The peculiar characteristics of the structure of CPL-7 muramidase correlate with its biochemical and biological properties. Whereas CPL-1, CPL-9 and the pneumococcal amidase strictly depend on the presence of choline-containing cell walls for activity, CPL-7 is able to degrade cell walls containing either choline or ethanolamine. These results support the previously postulated role for the C-terminal domain of these lytic enzymes in substrate recognition and provide further experimental evidence supporting the notion that the proteins have evolved by an exchange of modular units.
García
P
P
Centro de Investigaciones Biológicas, C.S.I.C., Madrid, Spain.
García
J L
JL
García
E
E
Sánchez-Puelles
J M
JM
López
R
R
D000595:Amino Acid Sequence; D001435:Bacteriophages / Q000201:enzymology / Q000235:genetics*; D001483:Base Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D005814:Genes, Viral; D008969:Molecular Sequence Data; D009113:Muramidase / Q000235:genetics* / Q000378:metabolism; D015183:Restriction Mapping; D013296:Streptococcus pneumoniae / Q000201:enzymology* / Q000235:genetics; D013379:Substrate Specificity; D015678:Viral Structural Proteins / Q000235:genetics
D015678:Viral Structural Proteins; D009113:Muramidase