Interaction between the bacterial nucleoid associated proteins Hha and H-NS involves a conformational change of Hha

The H-NS family of proteins plays a significant role in the regulation of gene expression in Gram-negative bacteria in response to various environmental factors. This study aims to elucidate the interaction details between the nucleoid-associated proteins Hha and H-NS. Using fluorescence anisotropy and NMR techniques, we investigate the binding dynamics of Hha with a truncated form of H-NS, specifically H-NS 64, which retains only the N-terminal dimerization domain. Our results indicate the formation of a complex between one Hha molecule and two H-NS 64 monomers at a NaCl concentration of 150 mM, suggesting that this complex serves as a nucleation point for larger aggregates. Additionally, NMR analyses reveal that Hha undergoes conformational changes, existing in a state of equilibrium between two distinct forms, one of which is stabilized upon binding to H-NS 64. Notably, similar dynamics are observed for Hha alone as temperature increases to 37 °C, hinting at the intrinsic conformational alterations of Hha playing a critical role in its interactions with H-NS.