CLEAVAGE OF SHIGELLA SURFACE PROTEIN VIRG OCCURS AT A SPECIFIC SITE, BUT THE SECRETION IS NOT ESSENTIAL FOR INTRACELLULAR SPREADING

被引：56

作者：

FUKUDA, I

SUZUKI, T

MUNAKATA, H

HAYASHI, N

KATAYAMA, E

YOSHIKAWA, M

SASAKAWA, C

机构：

[1] UNIV TOKYO, INST MED SCI, DEPT BACTERIOL, MINATO KU, TOKYO 108, JAPAN

[2] UNIV TOKYO, INST MED SCI, DEPT FINE MORPHOL, MINATO KU, TOKYO 108, JAPAN

[3] TOHOKU UNIV, SCH MED, DEPT BIOCHEM, AOBA KU, SENDAI, MIYAGI 980, JAPAN

来源：

JOURNAL OF BACTERIOLOGY | 1995年 / 177卷 / 07期

关键词：

D O I：

10.1128/jb.177.7.1719-1726.1995

中图分类号：

Q93 [微生物学];

学科分类号：

071005 ; 100705 ;

摘要：

The large plasmid-encoded outer membrane protein VirG (IcsA) of Shigella flexneri is essential for bacterial spreading by eliciting polar deposition of filamentous actin (F-actin) in the cytoplasm of epithelial cells'. Recent studies have indicated that VirG is located at one pole an the surface of the bacterium and secreted into the culture supernatant and that in host cells it is localized along the length of the F-actin tail. The roles of these VirG phenotypes in bacterial spreading still remain to be elucidated. In this study, we examined the surface-exposed portion of the VirG protein by limited trypsin digestion of S. flexneri YSH6000 and determined the sites for VirG processing during secretion into the culture supernatant. Our results indicated that the 85-kDa amino-terminal portion of VirG is located on the external side of the outer membrane, while the 37-kDa carboxy-terminal portion is embedded in it, The VirG cleavage required for release of the 85-kDa protein into the culture supernatant occurred at the Arg-Arg bond at positions 758 to 759. VirG-specific cleavage was observed iri Shigella species and enteroinvasive Escherichia coli, which requires an as yet unidentified protease activity governed by the virB gene on the large plasmid. To investigate whether the VirG-specific cleavage occurring in extracellular and intracellular bacteria is essential for VirG function in bacterial :spreading, the Arg-Arg cleavage site was modified to an Arg-Asp or Asp-Asp bond. The virG mutants thus constructed were capable of unipolar deposition of VirG on the bacterial surface but were unable to cleave VirG under in vitro or in vivo conditions. However, these mutants were still capable of eliciting aggregation of F-actin at one pole, spreading into adjacent cells, and giving rise to a positive Sereny test. Therefore, the ability to cleave and secrete VirG in Shigella species is not a prerequisite for intracellular spreading.

引用

页码：1719 / 1726

页数：8

共 40 条

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