VirB6 Is Required for Stabilization of VirB5 and VirB3 and Formation of VirB7 Homodimers in Agrobacterium tumefaciens

VirB6 from Agrobacterium tumefaciens is an essential component of the type IV secretion machinery for T pilus formation and genetic transformation of plants. Due to its predicted topology as a polytopic inner membrane protein, it was proposed to form the transport pore for cell-to-cell transfer of g...

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Główni autorzy: Hapfelmeier, Siegfried, Domke, Natalie, Zambryski, Patricia C., Baron, Christian
Format: Artykuł
Język:en
Wydane: American Society for Microbiology 2000
Hasła przedmiotowe:
Plant Microbiology
Dostęp online:https://ncbi.nlm.nih.gov/pmc/articles/PMC94622/
https://ncbi.nlm.nih.gov/pubmed/10913084
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spelling pubmed-946222002-09-13 VirB6 Is Required for Stabilization of VirB5 and VirB3 and Formation of VirB7 Homodimers in Agrobacterium tumefaciens Hapfelmeier, Siegfried Domke, Natalie Zambryski, Patricia C. Baron, Christian J Bacteriol Plant Microbiology VirB6 from Agrobacterium tumefaciens is an essential component of the type IV secretion machinery for T pilus formation and genetic transformation of plants. Due to its predicted topology as a polytopic inner membrane protein, it was proposed to form the transport pore for cell-to-cell transfer of genetic material and proteinaceous virulence factors. Here, we show that the absence of VirB6 leads to reduced cellular levels of VirB5 and VirB3, which were proposed to assist T pilus formation as minor component(s) or assembly factor(s), respectively. Overexpression of virB6 in trans restored levels of cell-bound and T pilus-associated VirB5 to wild type but did not restore VirB3 levels. Thus, VirB6 has a stabilizing effect on VirB5 accumulation, thereby regulating T pilus assembly. In the absence of VirB6, cell-bound VirB7 monomers and VirB7-VirB9 heterodimers were reduced and VirB7 homodimer formation was abolished. This effect could not be restored by expression of VirB6 in trans. Expression of TraD, a component of the transfer machinery of the IncN plasmid pKM101, with significant sequence similarity to VirB6, restored neither protein levels nor bacterial virulence but partly permitted T pilus formation in a virB6 deletion strain. VirB6 may therefore regulate T pilus formation by direct interaction with VirB5, and wild-type levels of VirB3 and VirB7 homodimers are not required. American Society for Microbiology 2000-08 /pmc/articles/PMC94622/ /pubmed/10913084 Text en Copyright © 2000, American Society for Microbiology
institution US National Library of Medicine
collection PubMed Central
language en
format Article
topic Plant Microbiology
spellingShingle Plant Microbiology
Hapfelmeier, Siegfried
Domke, Natalie
Zambryski, Patricia C.
Baron, Christian
VirB6 Is Required for Stabilization of VirB5 and VirB3 and Formation of VirB7 Homodimers in Agrobacterium tumefaciens
description VirB6 from Agrobacterium tumefaciens is an essential component of the type IV secretion machinery for T pilus formation and genetic transformation of plants. Due to its predicted topology as a polytopic inner membrane protein, it was proposed to form the transport pore for cell-to-cell transfer of genetic material and proteinaceous virulence factors. Here, we show that the absence of VirB6 leads to reduced cellular levels of VirB5 and VirB3, which were proposed to assist T pilus formation as minor component(s) or assembly factor(s), respectively. Overexpression of virB6 in trans restored levels of cell-bound and T pilus-associated VirB5 to wild type but did not restore VirB3 levels. Thus, VirB6 has a stabilizing effect on VirB5 accumulation, thereby regulating T pilus assembly. In the absence of VirB6, cell-bound VirB7 monomers and VirB7-VirB9 heterodimers were reduced and VirB7 homodimer formation was abolished. This effect could not be restored by expression of VirB6 in trans. Expression of TraD, a component of the transfer machinery of the IncN plasmid pKM101, with significant sequence similarity to VirB6, restored neither protein levels nor bacterial virulence but partly permitted T pilus formation in a virB6 deletion strain. VirB6 may therefore regulate T pilus formation by direct interaction with VirB5, and wild-type levels of VirB3 and VirB7 homodimers are not required.
author Hapfelmeier, Siegfried
Domke, Natalie
Zambryski, Patricia C.
Baron, Christian
author_facet Hapfelmeier, Siegfried
Domke, Natalie
Zambryski, Patricia C.
Baron, Christian
author_sort Hapfelmeier, Siegfried
title VirB6 Is Required for Stabilization of VirB5 and VirB3 and Formation of VirB7 Homodimers in Agrobacterium tumefaciens
title_short VirB6 Is Required for Stabilization of VirB5 and VirB3 and Formation of VirB7 Homodimers in Agrobacterium tumefaciens
title_full VirB6 Is Required for Stabilization of VirB5 and VirB3 and Formation of VirB7 Homodimers in Agrobacterium tumefaciens
title_fullStr VirB6 Is Required for Stabilization of VirB5 and VirB3 and Formation of VirB7 Homodimers in Agrobacterium tumefaciens
title_full_unstemmed VirB6 Is Required for Stabilization of VirB5 and VirB3 and Formation of VirB7 Homodimers in Agrobacterium tumefaciens
title_sort virb6 is required for stabilization of virb5 and virb3 and formation of virb7 homodimers in agrobacterium tumefaciens
publisher American Society for Microbiology
publisher_facet American Society for Microbiology
publishDate 2000
url https://ncbi.nlm.nih.gov/pmc/articles/PMC94622/
https://ncbi.nlm.nih.gov/pubmed/10913084
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