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Heterologous assembly of type IV pili by a type II secretion system reveals the role of minor pilins in assembly initiation
Author(s) -
Cisneros David A.,
PehauArnaudet Gerard,
Francetic Olivera
Publication year - 2012
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12033
Subject(s) - pilin , pilus , biology , fimbriae proteins , bacterial outer membrane , microbiology and biotechnology , escherichia coli , heterologous , pullulanase , genetics , gene , biochemistry , starch
Summary In G ram‐negative bacteria, type IV pilus assembly ( T4PS ) and type II secretion ( T2SS ) systems polymerize inner membrane proteins called major pilins or pseudopilins respectively, into thin filaments. Four minor pilins are required in both systems for efficient fibre assembly. E scherichia coli K ‐12 has a set of T4PS assembly genes that are silent under standard growth conditions. We studied the heterologous assembly of the E . coli type IV pilin PpdD by the K lebsiella oxytoca T2SS called the P ul system. PpdD pilus assembly in this context depended on the expression of the K . oxytoca minor pseudopilin genes pulHIJK or of the E . coli minor pilin genes ppdAB ‐ ygdB ‐ ppdC . The E . coli minor pilins restored assembly of the major pseudopilin PulG in a pulHIJK mutant, but not the secretion of the T2SS substrate pullulanase. Thus, minor pilins and minor pseudopilins are functionally interchangeable in initiating major pilin assembly, further extending the fundamental similarities between the two systems. The data suggest that, in both systems, minor pilins activate the assembly machinery through a common self‐assembly mechanism. When produced together, PulG and PpdD assembled into distinct homopolymers, establishing major pilins as key determinants of pilus elongation and structure.