# Synergy between acid stress chaperones HdeA and HdeB with clients and their key sites of activity

> **NIH NIH SC3** · CALIFORNIA STATE UNIVERSITY NORTHRIDGE · 2021 · $108,750

## Abstract

PROJECT SUMMARY / ABSTRACT
Background. Pathogenic bacteria must travel through the highly acidic environment of the stomach before
they can reach and infect the intestines. The stomach is therefore an important barricade which helps to kill
many bacteria before they can cause illness. In some of the most infectious bacteria, however, ATP-
independent chaperones HdeA and HdeB play major roles in aiding bacterial survival at low pH. Their job is to
protect other proteins from misfolding and aggregating as the cell transitions through the harsh environment of
the stomach and into the neutral environment of the intestines. HdeB is active at intermediate pH values, while
HdeA functions at the low pH typical of stomach acid. Although there are various models available to explain
the interplay between the two chaperones, it is still unclear which, if any, is correct.
Specific aims. The goal of the proposed work is to use NMR spectroscopy and other biophysical techniques
to pursue an in-depth investigation of the apparently synergistic mechanism by which the two chaperone
proteins operate and to probe the roles of specific residues that trigger or modify the activation of HdeA or
HdeB. Aim #1 is to examine the roles and interactions of HdeA and HdeB with chaperone clients as a function
of pH. Isotopic labeling and the unique properties of NMR spectroscopy will be employed to monitor each
protein individually within a mixture of HdeA, HdeB and a client protein, thereby providing different vantage
points to obtain unprecedented detail. Aim #2 is to probe sites of chaperone activation and stability in HdeA
and HdeB using targeted mutations. Here, a variety of techniques will be used to closely assess segments of
each protein that have been linked to essential roles in function and/or activation, including a key tryptophan in
the dimer interface of HdeB and the disulfide bond in HdeA, which helps to maintain the semi-folded structure
believed to be important to its chaperone function.
Health-related significance. Dysentery, caused by intestinal infection by pathogenic bacteria, kills at least
350,000 people per year worldwide. If we can elucidate the individual and collective roles of HdeA and HdeB in
the presence of client proteins, as well as the mechanistic importance of specific residues or regions, we can
better understand how these acid-stress chaperones help bacteria survive under extreme conditions. Improved
understanding can inform researchers designing vaccines or other therapeutics that can disable the activities
of HdeA and HdeB and thereby weaken the infectivity of these pathogenic bacteria.

## Key facts

- **NIH application ID:** 10334239
- **Project number:** 2SC3GM116745-05
- **Recipient organization:** CALIFORNIA STATE UNIVERSITY NORTHRIDGE
- **Principal Investigator:** KARIN A CROWHURST
- **Activity code:** SC3 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $108,750
- **Award type:** 2
- **Project period:** 2016-04-01 → 2025-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10334239

## Citation

> US National Institutes of Health, RePORTER application 10334239, Synergy between acid stress chaperones HdeA and HdeB with clients and their key sites of activity (2SC3GM116745-05). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10334239. Licensed CC0.

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