1.E.14 The LrgA Holin (LrgA Holin) Family
See 1.E for a generalized description of Holins.
LrgA is a 145 aa protein with 4 putative TMSs. It is a member of a large family of putative murine hydrolase exporters from a wide range of Gram-positive and Gram-negative bacteria as well as archaea. Most vary in size between 100 and 160 aas although a few are larger. It has been proposed that together with their homologues, CidAB (23% and 32% identical to LrgAB, respectively) are involved in programmed cell death in a process that is analogous to apoptosis in eukaryotes (Bayles, 2003). CidA, a 131 aa protein with 4 putative TMSs, is believed to be the holin which exports the autolysin CidB, while LrgA may be an antiholin. If this is a general mechanism for programmed cell death, this would explain their near ubiquity in the prokaryotic world. The cidABC operon is activated by CidR in the presence of acetic acid (Yang et al., 2005). LrgAB affect biofilm formation and oxidative stress and may be linked to competence in S. mutants (Ahn et al. 2012).