VirB7 and VirB9 Interactions Are Required for the Assembly and Antibacterial Activity of a Type IV Secretion System.
The type IV secretion system (T4SS) from the phytopathogen Xanthomonas citri (Xac) is a bactericidal nanomachine. The T4SS core complex is a ring composed of multiple copies of VirB7-VirB9-VirB10 subunits. Xac-VirB7 contains a disordered N-terminal tail (VirB7NT) that recognizes VirB9, and a C-terminal domain (VirB7CT) involved in VirB7 self-association. Here, we show that VirB7NTforms a short β strand upon binding to VirB9 and stabilizes it. A tight interaction between them is essential for T4SS assembly and antibacterial activity. Abolishing VirB7 self-association or deletion of the VirB7 C-terminal domain impairs this antibacterial activity without disturbing T4SS assembly. These findings reveal protein interactions within the core complex that are critical for the stability and activity of a T4SS.
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo 05508-000, Brazil.
Luciana Coutinho
LC
Oliveira
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo 05508-000, Brazil. Electronic address: diorge@iq.usp.br.
Diorge Paulo
DP
Souza
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo 05508-000, Brazil.
Gabriel Umaji
GU
Oka
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo 05508-000, Brazil.
Filipe da Silva
FDS
Lima
Departamento de Física, Instituto de Ciências Exatas e Naturais, Universidade Federal do Triângulo Mineiro, Uberaba, Minas Gerais 38064-200, Brazil.
Ronaldo Junio
RJ
Oliveira
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo 05508-000, Brazil.
Denize Cristina
DC
Favaro
NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht 3584-CH, the Netherlands.
Hans
H
Wienk
NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht 3584-CH, the Netherlands.
Rolf
R
Boelens
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo 05508-000, Brazil. Electronic address: chsfarah@iq.usp.br.
Chuck Shaker
CS
Farah
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo 05508-000, Brazil. Electronic address: roberto@iq.usp.br.
Roberto Kopke
RK
Salinas
D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D011485:Protein Binding; D055550:Protein Stability; D017433:Protein Structure, Secondary; D000069319:Type IV Secretion Systems / Q000737:chemistry / Q000378:metabolism*; D014974:Xanthomonas / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D000069319:Type IV Secretion Systems