Histone-like nucleoid-structuring protein (H-NS), is one of twelve nucleoid-associated proteins (NAPs)[1] whose main function is the organization of genetic material, including the regulation of gene expression via xenogeneic silencing.[2] H-NS is characterized by an N-terminal domain (NTD) consisting of two dimerization sites, a linker region that is unstructured and a C-terminal domain (CTD) that is responsible for DNA-binding.[2] Though it is a small protein (15 kDa),[3] it provides essential nucleoid compaction and regulation of genes (mainly silencing)[2] and is highly expressed, functioning as a dimer or multimer.[3] Change in temperature causes H-NS to be dissociated from the DNA duplex, allowing for transcription by RNA polymerase, and in specific regions lead to pathogenic cascades in enterobacteria such as Escherichia coli and the four Shigella species.[3]
Figure 1: The C-terminal domain (CTD)[4] is also known as the DNA-binding domain. H-NS NTD's oligomerize with each other while the CTD binds to specific regions of DNA containing a specific topology called a TpA step.[2] Aromatic amino acid residues are labelled in gray, negatively charged particles are displayed in red, and positively charged particles are labelled in teal. H-bond lengths are displayed in magenta.