A Novel H-NS-like protein from an antarctic psychrophilic bacterium reveals a crucial role for the N-terminal domain in thermal stability.
We describe here new members of the H-NS protein family identified in a psychrotrophic Acinetobacter spp. bacterium collected in Siberia and in a psychrophilic Psychrobacter spp. bacterium collected in Antarctica. Both are phylogenetically closely related to the HvrA and SPB Rhodobacter transcriptional regulators. Their amino acid sequence shares 40% identity, and their predicted secondary structure displays a structural and functional organization in two modules similar to that of H-NS in Escherichia coli. Remarkably, the Acinetobacter protein fully restores to the wild-type H-NS-dependent phenotypes, whereas the Psychrobacter protein is no longer able to reverse the effects of H-NS deficiency in an E. coli mutant strain above 30 degrees C. Moreover, in vitro experiments demonstrate that the ability of the Psychrobacter H-NS protein to bind curved DNA and to form dimers is altered at 37 degrees C. The construction of hybrid proteins containing the N- or the C-terminal part of E. coli H-NS fused to the C- or N-terminal part of the Psychrobacter protein demonstrates the role of the N-terminal domain in this process. Finally, circular dichroism analysis of purified H-NS proteins suggests that, as compared with the E. coli and Acinetobacter proteins, the alpha-helical domain displays weaker intermolecular interactions in the Psychrobacter protein, which may account for the low thermal stability observed at 37 degrees C.
Tendeng
Christian
C
Unité de Génétique des Génomes Bactériens, Institut Pasteur, 75724 Paris Cedex 15, France.
Krin
Evelyne
E
Soutourina
Olga A
OA
Marin
Antoine
A
Danchin
Antoine
A
Bertin
Philippe N
PN
D000150:Acinetobacter / Q000737:chemistry*; D000595:Amino Acid Sequence; D000864:Antarctic Regions; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D002942:Circular Dichroism; D003080:Cold Temperature; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D019281:Dimerization; D004355:Drug Stability; D004926:Escherichia coli / Q000737:chemistry; D020563:Gammaproteobacteria / Q000737:chemistry*; D006358:Hot Temperature; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D016354:Rhodobacter capsulatus / Q000737:chemistry; D012242:Rhodobacter sphaeroides / Q000737:chemistry; D016415:Sequence Alignment; D012800:Siberia; D013329:Structure-Activity Relationship
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C031908:H-NS protein, bacteria; D004247:DNA