Characterization of Escherichia coli type 1 pilus mutants with altered binding specificities

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Adhesion

Background:

• Escherichia coli type 1 pili utilize the FimH adhesin protein for cellular attachment.
• The FimH adhesin's binding properties are crucial for E. coli pathogenesis and colonization.
• Understanding FimH-mediated interactions is key to developing anti-adhesion strategies.

Purpose of the Study:

• To generate and characterize mutants of the FimH adhesin protein.
• To investigate the impact of specific fimH gene lesions on FimH binding specificity.
• To explore the structural and functional consequences of mutations within the FimH binding pocket.

Main Methods:

• Polymerase chain reaction (PCR) mutagenesis was employed to introduce specific mutations into the fimH gene.
• A novel enrichment strategy was developed to isolate and select mutants with altered binding phenotypes.
• Genetic sequencing was used to confirm single-lesion mutations in the fimH gene.

Main Results:

• Two distinct mutants, each with a single amino acid substitution in FimH, were successfully generated.
• Both mutants exhibited altered binding profiles, deviating from the wild-type FimH cell type specificity.
• One mutation affected a known temperature-dependent binding site, while the other was located within the predicted FimH binding pocket.

Conclusions:

• Single amino acid changes in FimH can significantly alter its binding specificity.
• The FimH binding pocket and temperature-sensitive regions are critical determinants of adhesin-host interactions.
• These findings provide insights into the structure-function relationships of FimH and potential targets for therapeutic intervention.