1.E.24 The Bacterophase Dp-1 Holin (Dp-1 Holin) Family
The genes coding for the lytic system of the pneumococcal phage, Dp-1, has been cloned and characterized (Sheehan et al., 1997). The lytic enzyme of this phage (Pal), an N-acetyl-muramoyl-L-alanine amidase, shows a modular organization similar to that described for the lytic enzymes of Streptococcus pneumoniae and its bacteriophages. The construction of chimeric enzymes between pneumococcus and bacteria (or phages) that belong to different Gram-positive families has shown that the interchange of functional domains switches enzyme specificity.
The holin of phage Dp-1 is 74 aas long with two probable TMSs (residues 12-32 and 39-57). It shows sequence similarity (30% identity) with a holin encoded within the genone of Enterococcus faecalis (Paulsen et al., 2003). Several Gram-positive bacteria and their phage also possess this family of holins, representatives of which are listed in the table.