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Updated: Feb 10, 2026

Assessing Respiratory Immune Responses to Haemophilus Influenzae
Published on: June 29, 2021
Characterization of a nontypeable Haemophilus influenzae thermonuclease
Christine Cho1,2,3, Aroon T Chande4,5,6, Lokesh Gakhar7,8
1Iowa Inflammation Program, The University of Iowa, Iowa City, Iowa City, IA, United States of America.
Abstract:
Nontypeable Haemophilus influenzae (NTHi) has been shown to form biofilms, comprised of extracellular DNA (eDNA), in the middle ear and bronchus during clinical infections. Studies in our laboratory have shown that NTHi possesses a homolog of Staphylococcus aureus thermonuclease (staphylococcal thermonuclease), NTHi nuclease (NTHi Nuc, HI_1296). This enzyme had similar size, heat stability, and divalent cation requirements to those of the staphylococcal homolog as determined by light scattering and circular dichroism spectroscopy. Small angle X-ray scattering (SAXS) analysis suggested an overall shape and substrate-binding site comparable to those of staphylococcal nuclease. However, NTHi Nuc was approximately 25-fold more active in fluorescence resonance energy transfer (FRET) activity assay than staphylococcal thermonuclease. Homology modeling implicates shorter NTHi Nuc loops near the active site for this enhanced activity.
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