# Regulation and localization of flp pili: an under-investigated system

> **NIH NIH R15** · UNIVERSITY OF MISSISSIPPI · 2020 · $414,567

## Abstract

PROJECT SUMMARY
 Pili are bacterial surface structures that are used by bacteria in many ways. They can be used for
motility, genetic exchange, and surface attachment, and are often critical virulence factors for pathogens. A
particular type of pilus, the flp pilus, is found in many bacterial pathogens, including Vibrio vulnificus and
Aggregatibacter actinomycetemcomitans, and is used by some members of the human microbiome to
establish permanence in the intestinal tract. Despite its importance, the flp pilus is not nearly studied to the
depth of other pilus systems, and has many unexplored facets and curiosities. In this proposal we outline
experiments to explore the flp pilus using a model bacterium that provides many technical benefits for studying
pili: Caulobacter crescentus. A common characteristic of the flp system is that the pilin gene is regulated
separately from the rest of the pilus genes. In C. crescentus, the transcriptional activator CtrA binds to four
sites in the pilin promoter. Preliminary data indicates that one site induces expression, while the remaining
sites inhibit and/or delay transcription from their upstream positions, a phenomenon not previously reported in
bacteria. Regulation of the pilin promoter will be explored by mutating different CtrA-binding sites and
measuring changes in expression timing and magnitude. The direct interaction and potential cooperativity of
CtrA binding at the pilin promoter will be assessed using biochemical assays. Lastly, regulation of the pilin
subunit will be altered by mutagenesis, and the effect of differential regulation of the pilin subunit and how it
contributes to pilus synthesis as well as physiological consequences such as phage infection and surface
attachment will be examined (Aim 1). Another common characteristic of the flp pilus is that it is often polarly
localized. Localization depends on the TadZ protein, but how that protein is localized is a mystery. Protein
interaction techniques will be used to identify and characterize the factors that cause TadZ, and thus the flp
pilus, to become polarly localized. Additionally, the entire protein complement of the flp pilus in this organism
will be determined by purification of whole intact pili using a novel purification strategy, something that has
never before been accomplished (Aim 2). These studies will provide insight into features conserved among flp
pili systems, and thus provide insight into a structure important for many human pathogenic and commensal
organisms.

## Key facts

- **NIH application ID:** 10046802
- **Project number:** 1R15GM139127-01
- **Recipient organization:** UNIVERSITY OF MISSISSIPPI
- **Principal Investigator:** Patrick David Curtis
- **Activity code:** R15 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $414,567
- **Award type:** 1
- **Project period:** 2020-08-01 → 2023-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10046802

## Citation

> US National Institutes of Health, RePORTER application 10046802, Regulation and localization of flp pili: an under-investigated system (1R15GM139127-01). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10046802. Licensed CC0.

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