The structural and functional organization of H‐NS‐like proteins is evolutionarily conserved in Gram‐negative bacteria

Abstract

SummaryThe structural gene of the H-NS protein, a global regulator of bacterial metabolism, has been identified in the group of enterobacteria as well as in closely related bacteria, such as Erwinia chrysanthemi and Haemophilus influenzae. Isolated outside these groups, the BpH3 protein of Bordetella pertussis exhibits a low amino acid conservation with H-NS, particularly in the N-terminal domain. To obtain information on the structure, function and/or evolution of H-NS, we searched for other H-NS-related proteins in the latest databases. We found that HvrA, a trans-activator protein in Rhodobacter capsulatus, has a low but significant similarity with H-NS and H-NS-like proteins. This Gram-negative bacterium is phylogenetically distant from Escherichia coli. Using theoretical analysis (e.g. secondary structure prediction and DNA binding domain modelling) of the amino acid sequence of H-NS, StpA (an H-NS-like protein in E. coli ), BpH3 and HvrA and by in vivo and in vitro experiments (e.g. complementation of various H-NS-related phenotypes and competitive gel shift assay), we present evidence that these proteins belong to the same class of DNA binding proteins. In silico analysis suggests that this family also includes SPB in R. sphaeroides, XrvA in Xanthomonas oryzae and VicH in Vibrio cholerae. These results demonstrate that proteins structurally and functionally related to H-NS are widespread in Gram-negative bacteria.

MvaT proteins in Pseudomonas spp.: a novel class of H-NS-like proteins

“…jouy.inra.fr), this domain was predicted to share the same three-dimensional structure as the E. coli H-NS C-domain resolved previously by NMR (Shindo et al, 1995). Finally, the expression of the strain Y1000 protein structural gene in an E. coli mutant fully reversed additional hns-related phenotypes, for example, the loss of motility on semi-solid medium and the ability to use b-glucoside as a sole carbon source, as observed previously with other H-NS-like proteins (Goyard & Bertin, 1997;Bertin et al, 1999Bertin et al, , 2001Tendeng et al, 2000). This strongly suggests that the protein we characterized belongs to the H-NS family and shares the same structural and functional organization as members of this family despite the unusually low amino acid conservation.…”

“…Except for enterobacteria, where H-NS has been shown to control the expression of many genes, for example, in E. coli , the role in bacterial physiology of most H-NS-related proteins remains unknown. However, they constitute a family of proteins displaying an evolutionarily conserved structural and functional organization in two modules (Dorman et al, 1999;Bertin et al, 1999). The N-terminal oligomerization domain displays strong amino acid sequence divergence but is predicted to adopt an a-helix structure in all H-NS proteins , consistent with the recent three-dimensional structure of this domain in H-NS of E. coli (Renzoni et al, 2001;Bloch et al, 2003).…”

A role for histone-like protein H1 (H-NS) in the regulation of hemolysin expression by Serratia marcescens

“…Despite the functional similarity between E. coli and S. marcescens H-NS, the mechanism by which H-NS modulates S. marcescens hemolysin is not clear. Previous studies have shown that H-NS can alter DNA supercoiling and that variation of DNA supercoiling may modulate expression of virulence genes in response to the same environmental factors (17). We have shown that environmental factors such as pH, osmolarity and growth phase affect hemolysin expression in hns mutants and in wild-type strains.…”

“…Our data also suggest that E. coli H-NS may also be involved in the regulation of the S. marcescens hemolysin operon. This finding is not surprising since the sequence of E. coli H-NS and S. marcescens H-NS appears to be highly conserved (17). Despite the functional similarity between E. coli and S. marcescens H-NS, the mechanism by which H-NS modulates S. marcescens hemolysin is not clear.…”

“…The ability of bacteria to persist in the human host depends upon prompt adaptation to changing environmental conditions such as temperature, pH, osmolarity, oxygen tension, and nutrients (16,17). Previous studies have suggested that certain environmental factors and the action of H-NS on the nucleoid modulate the expression of several virulence genes (6,7).…”