The Vibrio cholerae Minor Pilin TcpB Initiates Assembly and Retraction of the Toxin-Coregulated Pilus

PLoS Pathogens

Nicolas Biais¹  Rajan Lala¹  Ingrid Spielman¹  Yang Gao²  Caitlyn A. Hauke²  Jarrad M. Marles²  Gabriela Kovacikova²  Ronald K. Taylor²  Subramania Kolappan³  Tony Harn³  Dixon Ng³  Tuba Altindal³  Zia Verjee³  Lisa Craig⁴ 

[1] Biology Department, Brooklyn College, City University of New York, Brooklyn, New York, United States of America;Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America;Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada;Graduate Center, City University of New York, Brooklyn, New York, United States of America

关键词: Pili;    fimbriae;    Vibrio cholerae;    Secretion;    Immunoblotting;    Adenosine triphosphatase;    Secretin;    Cell cultures;    Neisseria gonorrhoeae;   

DOI  :  10.1371/journal.ppat.1006109

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Type IV pilus (T4P) systems are complex molecular machines that polymerize major pilin proteins into thin filaments displayed on bacterial surfaces. Pilus functions require rapid extension and depolymerization of the pilus, powered by the assembly and retraction ATPases, respectively. A set of low abundance minor pilins influences pilus dynamics by unknown mechanisms. The Vibrio cholerae toxin-coregulated pilus (TCP) is among the simplest of the T4P systems, having a single minor pilin TcpB and lacking a retraction ATPase. Here we show that TcpB, like its homolog CofB, initiates pilus assembly. TcpB co-localizes with the pili but at extremely low levels, equivalent to one subunit per pilus. We used a micropillars assay to demonstrate that TCP are retractile despite the absence of a retraction ATPase, and that retraction relies on TcpB, as a V. cholerae tcpB Glu5Val mutant is fully piliated but does not induce micropillars movements. This mutant is impaired in TCP-mediated autoagglutination and TcpF secretion, consistent with retraction being required for these functions. We propose that TcpB initiates pilus retraction by incorporating into the growing pilus in a Glu5-dependent manner, which stalls assembly and triggers processive disassembly. These results provide a framework for understanding filament dynamics in more complex T4P systems and the closely related Type II secretion system.

【 授权许可】

CC BY