New roles for key residues in helices H1 and H2 of the Escherichia coli H-NS N-terminal domain: H-NS dimer stabilization and Hha binding |
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Authors: | García Jesús Madrid Cristina Juárez Antonio Pons Miquel |
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Institution: | Laboratory of Biomolecular NMR, Institut de Recerca Biomèdica-Parc Científic de Barcelona, Josep Samitier, 1-5 08028 Barcelona, Spain. |
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Abstract: | Bacterial nucleoid-associated proteins H-NS and Hha modulate gene expression in response to environmental factors. The N-terminal domain of H-NS is involved in homomeric and heteromeric protein-protein interactions. Homomeric interaction leads to the formation of dimers and higher oligomers. Heteromeric interactions with Hha-like proteins modify the modulatory properties of H-NS. In this study, we have used NMR and mutagenesis of the N-terminal domain of H-NS to identify the Hha-binding region around helices H1 and H2 of H-NS. Two conserved arginine residues, R12 and R15, located in the same side and in adjacent turns of helix H2 are shown to be involved in two different protein-protein interactions: R12 is essential for Hha binding and does not affect H-NS dimer formation, and R15 does not affect Hha binding but is essential for the proper folding of H-NS dimers. Our results demonstrate a close structural connection between Hha-H-NS interactions and H-NS dimerization that may be involved in a possible mechanism for the modulation of the H-NS regulatory activity by Hha. |
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Keywords: | nucleoid-associated proteins protein-protein interactions protein NMR H-NS mutagenesis Hha |
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