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Donor strand complementation governs intersubunit interaction of fimbriae of the alternate chaperone pathway
Author(s) -
Poole Steven T.,
McVeigh Annette L.,
Anantha Ravi P.,
Lee Lanfong H.,
Akay Yasemin M.,
Pontzer Emily A.,
Scott Daniel A.,
Bullitt Esther,
Savarino Stephen J.
Publication year - 2007
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/j.1365-2958.2007.05612.x
Subject(s) - fimbria , periplasmic space , enterotoxigenic escherichia coli , biology , bacterial adhesin , pilus , complementation , protein subunit , immunoelectron microscopy , chaperone (clinical) , escherichia coli , bacterial outer membrane , microbiology and biotechnology , genetics , mutant , antibody , gene , medicine , pathology , enterotoxin
Summary Fimbrial filaments assembled by distinct chaperone pathways share a common mechanism of intersubunit interaction, as elucidated for colonization factor antigen I (CFA/I), archetype of enterotoxigenic Escherichia coli (ETEC) Class 5 fimbriae. We postulated that a highly conserved β‐strand at the major subunit N‐terminus represents the donor strand, analogous to interactions within Class I pili. We show here that CFA/I fimbriae utilize donor strand complementation to promote proper folding of and interactions between CFA/I subunits. We constructed a series of genetic variants of CfaE, the CFA/I adhesin, incorporating a C‐terminal extension comprising a flexible linker and 10–19 of the N‐terminal residues of CfaB, the major subunit. Variants with a donor strand complement (dsc) of ≥ 12 residues were recoverable from periplasmic fractions. Genetic disruption of the donor β‐strand reduced CfaE recovery. A hexahistidine‐tagged variant of dsc 19 CfaE formed soluble monomers, folded into β‐sheet conformation, displayed adhesion characteristic of CFA/I, and elicited antibodies that inhibited mannose‐resistant haemagglutination by ETEC expressing CFA/I, CS4 and CS14 fimbriae. Immunoelectron microscopy indicated that CfaE was confined to the distal fimbrial tip. Our findings provide the basis to elucidate structure and function of this class of fimbrial adhesins and assess the feasibility of an adhesin‐based vaccine.