1.E.7 The HP1 Holin (HP1 Holin) Family
See 1.E for a generalized description of Holins.
The NucE protein in Serratia marcescens shows homology to phage holin proteins involved in releasing lysozyme to the peptidoglycan of Gram-negative bacteria. The protein contains two characteristic TMSs with a positively charged C-terminus. When the nucC operon carrying the nucEDC genes is placed in the Escherichia coli chromosome, NucE functions as a holin. Additionally, NucE can complement lysis-defective bacteriophage mutants to allow for plaque formation and release of phage. Although NucE can function as a holin it is not involved in the transport of nuclease, an extracellular protein encoded by the nucA gene.
The proteins of 1.E.7 show some sequence similarity with those of family 1.E.1