Molecular basis for the maintenance of envelope integrity in Selenomonas ruminantium: Controlled mechanism of cadaverine biosynthesis which covalently links to the peptidoglycan

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Selenomonas ruminantium has cadaverine(Cad),which links covalently to the peptidoglycan (PG) for the cell devision.In this bacterium,Cad is synthesized constitutively from L-lysine by lysine/ornithine decarboxylase (LDC/ODC) and transferred to PG. Here,we found that (1) LDC/ODC was degraded at an early stationary phase by ATP dependent ClpXP.This degradation requires a ribosomal protein L10 which is induced into cytoplasm by putrescine in the cells. The induced L10 has similar biochemical and biophysical characteristics to those of an antizyme (AZ),which have been reported only in mammalian cells.(2) PG-bound Cad mediates an interaction between PG and the periplasm-exposed S-layer homologous domain of Mep45, a major outer membrane (OM) protein of this bacterium, thereby forms the structural linkage between the PG and OM.(3)The gene of lipid intermediate:diamine transferase (Ldt) for cadaverine-adding reaction into the lipid intermediate was cloned and the gene product was purified.