13C, 15N and 1H backbone and side chain chemical shift assignment of acid-stress bacterial chaperone HdeA at pH 6
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HdeA is a small chaperone found in the periplasm of several common pathogenic bacteria (Escherichia coli, Shigella flexneri and Brucella abortus) which are the leading causes of dysentery worldwide, especially in developing countries. Its job is to protect other periplasmic proteins from aggregating as the bacteria pass through the low pH environment of the human stomach on their way to infect the intestines. HdeA is an inactive folded dimer at neutral pH, but becomes a disordered active monomer at pH < 3. To initiate NMR characterization of HdeA at pH 6, 94 % of the backbone and 86 % of the side chain chemical shifts have been assigned. The loop linking helices B and C remains largely unassigned due to missing peaks in the 1H–15N HSQC and other spectra, most likely due to intermediate timescale chemical exchange. Many of the weakest intensity backbone peaks correspond to residues that surround this loop within the tertiary structure. Assignment experiments have therefore helped to provide preliminary clues about the region of the protein that may be most responsible for initiating unfolding as the pH drops, and constitute an important first step in improving our understanding of, and ultimately combatting, HdeA activity.
KeywordsHdeA Escherichia coli Chaperone NMR Chemical shift assignment
The author would like to thank Dr. James Bardwell (University of Michigan) for kindly providing the HdeA-expressing plasmid, as well as the Department of Chemistry & Biochemistry and the College of Science and Mathematics at CSU Northridge for research support. The experiments were performed on a 600 MHz NMR spectrometer generously funded by NSF MRI grant CHE-1040134.
Conflict of interest
The author declares that she has no conflict of interest in the publication of this manuscript.
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