Frandi Antonio, Jacquier Nicolas, Théraulaz Laurence, Greub Gilbert, Viollier Patrick H
Department of Microbiology and Molecular Medicine, Institute of Genetics and Genomics in Geneva (iGE3), Faculty of Medicine/CMU, University of Geneva, Rue Michel Servet 1, 1211 Genève 4, Switzerland.
Center for Research on Intracellular Bacteria (CRIB), Institute of Microbiology, University Hospital Center and University of Lausanne, Bugnon 48, 1011 Lausanne, Switzerland.
Nat Commun. 2014 Jun 23;5:4200. doi: 10.1038/ncomms5200.
The nature and assembly of the chlamydial division septum is poorly defined due to the paucity of a detectable peptidoglycan (PG)-based cell wall, the inhibition of constriction by penicillin and the presence of coding sequences for cell wall precursor and remodelling enzymes in the reduced chlamydial (pan-)genome. Here we show that the chlamydial amidase (AmiA) is active and remodels PG in Escherichia coli. Moreover, forward genetics using an E. coli amidase mutant as entry point reveals that the chlamydial LysM-domain protein NlpD is active in an E. coli reporter strain for PG endopeptidase activity (ΔnlpI). Immunolocalization unveils NlpD as the first septal (cell-wall-binding) protein in Chlamydiae and we show that its septal sequestration depends on prior cell wall synthesis. Since AmiA assembles into peripheral clusters, trimming of a PG-like polymer or precursors occurs throughout the chlamydial envelope, while NlpD targets PG-like peptide crosslinks at the chlamydial septum during constriction.
由于缺乏可检测到的基于肽聚糖（PG）的细胞壁、青霉素对收缩的抑制作用以及衣原体简化（泛）基因组中细胞壁前体和重塑酶编码序列的存在，衣原体分裂隔膜的性质和组装情况尚不明确。在此，我们表明衣原体酰胺酶（AmiA）具有活性，并能在大肠杆菌中重塑PG。此外，以大肠杆菌酰胺酶突变体为切入点进行的正向遗传学研究表明，衣原体LysM结构域蛋白NlpD在用于PG内肽酶活性的大肠杆菌报告菌株（ΔnlpI）中具有活性。免疫定位揭示NlpD是衣原体中首个隔膜（细胞壁结合）蛋白，并且我们表明其在隔膜处的隔离取决于先前的细胞壁合成。由于AmiA组装成外周簇，因此在整个衣原体包膜中都会发生类PG聚合物或前体的修剪，而NlpD在收缩过程中靶向衣原体隔膜处的类PG肽交联。
