García Jesús, Madrid Cristina, Juárez Antonio, Pons Miquel
Laboratory of Biomolecular NMR, Institut de Recerca Biomèdica-Parc Científic de Barcelona, Josep Samitier, 1-5 08028 Barcelona, Spain.
J Mol Biol. 2006 Jun 9;359(3):679-89. doi: 10.1016/j.jmb.2006.03.059. Epub 2006 Apr 18.
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.
细菌类核相关蛋白H-NS和Hha可根据环境因素调节基因表达。H-NS的N端结构域参与同聚和异聚蛋白-蛋白相互作用。同聚相互作用导致二聚体和更高聚体的形成。与Hha样蛋白的异聚相互作用改变了H-NS的调节特性。在本研究中，我们利用核磁共振（NMR）和对H-NS N端结构域进行诱变，以确定H-NS的H1和H2螺旋周围的Hha结合区域。位于H2螺旋同一侧且相邻转角处的两个保守精氨酸残基R12和R15，参与了两种不同的蛋白-蛋白相互作用：R12对Hha结合至关重要，且不影响H-NS二聚体的形成；R15不影响Hha结合，但对H-NS二聚体的正确折叠至关重要。我们的结果表明，Hha-H-NS相互作用与H-NS二聚化之间存在紧密的结构联系，这可能参与了Hha调节H-NS调节活性的一种可能机制。
