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

反刍月形单胞菌（Selenomonasruminantium）具有与肽聚糖（PG）共价连接的尸胺（cadaine，Cad），在该细菌中，Cad通过赖氨酸/鸟氨酸脱羧酶（Lysine/Ornithine decarboxylase，LDC/ODC）由L-赖氨酸组成型合成并转移到PG。我们发现（1）LDC/ODC在ATP依赖性ClpXP的作用下，在稳定期早期被降解，这种降解需要一种核糖体蛋白L10，该蛋白被腐胺诱导进入细胞质在细胞中。诱导的L10具有类似的生物化学和生物物理特性的抗酶（AZ），这已被报道只在哺乳动物细胞。(2)PG结合的Cad介导PG和Mep 45的周质暴露的S层同源结构域之间的相互作用，Mep 45是该细菌的主要外膜（OM）蛋白，从而形成PG和OM之间的结构连接。（3）克隆了脂质中间体二胺转移酶（Ldt）的基因，并纯化了基因产物。

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.