Cadaverine Covalently Linked to Peptidoglycan Is Required for Interaction between the Peptidoglycan and the Periplasm-Exposed S-Layer-Homologous Domain of Major Outer Membrane Protein Mep45 in Selenomonas ruminantium
Cadaverine Covalently Linked to Peptidoglycan Is Required for Interaction between the Peptidoglycan and the Periplasm-Exposed S-Layer-Homologous Domain of Major Outer Membrane Protein Mep45 in Selenomonas ruminantium
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DOI：
10.1128/jb.00417-10
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发表时间：
2010-11-01
影响因子：
3.2
通讯作者：
Kamio, Yoshiyuki
中科院分区：
文献类型：
--
作者：
Kojima, Seiji;Ko, Kyong-Cheol;Kamio, Yoshiyuki
反式单胞菌的肽聚糖与身体碱(PG-CADVERINE)共价结合，在维持细胞表面结构的完整性方面可能起着重要作用。这种细菌的外膜含有一个45 kDa的主要蛋白(Mep45)，它是一种推测的肽聚糖相关蛋白。在这份报告中，我们测定了mep45基因的核苷酸序列，并研究了Pg-Cadverine、Mep45与细胞表面结构的关系。氨基酸序列分析表明，Mep45由N-端的S层同源结构域、α-螺旋卷曲结构域和C-端的富含β链的区域组成。N-末端的SLH结构域突出到周质间隙，负责与肽聚糖结合。已确定Mep45以一种依赖于PG-Cadverine的存在的方式与肽聚糖结合。电子显微镜显示，缺陷的PG-身体碱减少了肽聚糖与外膜之间的结构相互作用，这与PG-身体碱所起的作用是一致的。Mep45的C末端富含β链的区域被预测为14链β桶结构的膜结合单位。在这里，我们认为PG-Cadverine具有重要的功能，通过与Mep45的SLH结构域的特异性相互作用，促进肽聚糖与外膜之间的结构连接。
The peptidoglycan of Selenomonas ruminantium is covalently bound to cadaverine (PG-cadaverine), which likely plays a significant role in maintaining the integrity of the cell surface structure. The outer membrane of this bacterium contains a 45-kDa major protein (Mep45) that is a putative peptidoglycan-associated protein. In this report, we determined the nucleotide sequence of the mep45 gene and investigated the relationship between PG-cadaverine, Mep45, and the cell surface structure. Amino acid sequence analysis showed that Mep45 is comprised of an N-terminal S-layer-homologous (SLH) domain followed by alpha-helical coiled-coil region and a C-terminal beta-strand-rich region. The N-terminal SLH domain was found to be protruding into the periplasmic space and was responsible for binding to peptidoglycan. It was determined that Mep45 binds to the peptidoglycan in a manner dependent on the presence of PG-cadaverine. Electron microscopy revealed that defective PG-cadaverine decreased the structural interactions between peptidoglycan and the outer membrane, consistent with the proposed role for PG-cadaverine. The C-terminal beta-strand-rich region of Mep45 was predicted to be a membrane-bound unit of the 14-stranded beta-barrel structure. Here we propose that PG-cadaverine possesses functional importance to facilitate the structural linkage between peptidoglycan and the outer membrane via specific interaction with the SLH domain of Mep45.