title: 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.
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.
authors.affiliation: Laboratory of Biomolecular NMR, Institut de Recerca Biomèdica-Parc Científic de Barcelona, Josep Samitier, 1-5 08028 Barcelona, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: García
authors.forename: Cristina
authors.initials: C
authors.lastname: Madrid
authors.forename: Antonio
authors.initials: A
authors.lastname: Juárez
authors.forename: Miquel
authors.initials: M
authors.lastname: Pons
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000737:chemistry*; D019281:Dimerization; D004926:Escherichia coli / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C031908:H-NS protein, bacteria; D011994:Recombinant Proteins; D001120:Arginine