Part:BBa_K2570016

hns

The H-NS protein from E.coli is a highly charged 137-amino acid residue (M,= 15,500) polypeptide that exists in solution predominantly as a homodimer due to strong hydrophobic interactions between the subunits. H-NS binds with high affinity but low sequence specificity to double-stranded linear or circular DNA and displays a certain preference for curved DNA segments. Binding of H-NS in vitro to circular closed plasmid DNA results in a compaction of its substrate without a strong effect on the linking number, and its overproduction in vivo results in a striking condensation of the bacterial chromosomal DNA.

The cellular functions of H-NS have recently found widespread attention, since mutations in its structural gene show highly pleiotropic phenotypes. The hns gene has been genetically and physically mapped to the 27.5-min region of the E.coli chromosome, and independently isolated mutations in this gene have been designated bglY, pilG, virR, and osmZ. Mutations in hns lead to changes in gene expression, influence genetic recombination, affect bacterial virulence, decrease the motility of the bacterial cell , increase the formation of chromosomal deletions , and stimulate the transposition of bacteriophage Mu. Both increases and decreases in the rate of synthesis of a sizable number of proteins are observed in hns mutants.

One of the best studied systems whose transcription is strongly affected by H-NS is the proU operon, which encodes a binding protein-dependent transport system for the osmoprotectant glycine betaine. Transcription of the proU operon (proV, proW, and pro X ) is sensitively determined by the osmolarity of the environment. The basal transcription of proU is very low and is strongly stimulated upon a sudden osmotic upshock its elevated level of transcription at high osmolarity is proportional to the osmolarity of the growth medium. One of the factors that determine the level of proU expression is the H-NS protein. Mutations in the hns structural gene result in a strong increase of proU transcription, but do not abolish osmoregulation of proU expression.

Fig.1 H-NS DNA binding domain (POB ID: 1HNR).

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  COMPATIBLE WITH RFC[21]
• 23
  COMPATIBLE WITH RFC[23]
• 25
  COMPATIBLE WITH RFC[25]
• 1000
  INCOMPATIBLE WITH RFC[1000]

  Illegal SapI.rc site found at 154