Hfq protein

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Hfq protein with a bound sRNA.

The Hfq protein (also known as HF-I protein) encoded by the hfq gene was discovered in 1968 as an

bacteriophage Qβ.[1] It is now clear that Hfq is an abundant bacterial RNA binding protein which has many important physiological roles that are usually mediated by interacting with Hfq binding sRNA
.

In E. coli, Hfq mutants show multiple stress response related phenotypes.

Enterobacteria.[3][4][5] It also regulates sRNA in Vibrio cholerae, a specific example being MicX sRNA.[6]
In
CLIP-Seq study of Hfq in Salmonella has revealed 640 binding sites across the Salmonella transcriptome. The majority of these binding sites was found in mRNAs and sRNAs.[9]
In Photorhabdus luminescens, a deletion of the hfq gene causes loss of secondary metabolite production.[10]

Hfq mediates its pleiotropic effects through several mechanisms. It

antisense interaction with their targets. It also acts independently to modulate mRNA decay (directing mRNA transcripts for degradation) and also acts as a repressor of mRNA translation. Genomic SELEX has been used to show that Hfq binding RNAs are enriched in the sequence motif 5'-AAYAAYAA-3'.[11] Hfq was also found to act on ribosome biogenesis in E. coli, specifically on the 30S subunit. Hfq mutants accumulate higher levels of immature small subunits and decreased translation accuracy.[12] This function on the bacterial ribosome could also account for the pleiotropic effect typical of Hfq deletion strains.[13]

Electron microscopy imaging reveals that, in addition to the expected localization of this protein in cytoplasmic regions and in the nucleoid, an important fraction of Hfq is located in close proximity to the membrane.[14]

Crystallographic structures

Six crystallographic structures of 4 different Hfq proteins have been published so far;

P. aeruginosa Hfq in a low salt condition (1U1S​) and a high salt condition (1U1T​), Hfq from S. aureus with bound RNA (1KQ2​) and without (1KQ1​), and the Hfq(-like) protein from M. jannaschii (2QTX
​).

All six structures confirm the hexameric ring-shape of a Hfq protein complex.

See also

References

  1. PMID 4315363
    .
  2. S2CID 46245659
    .
  3. PMID 8654929
    .
  4. PMID 17158661
    .
  5. PMID 8682778
    .
  6. PMID 17590231
    .
  7. PMID 17163975
    .
  8. PMID 16999834
    .
  9. PMID 27044921
    .
  10. S2CID 6541706
    .
  11. PMID 20348540
    .
  12. PMID 29669858
    .
  13. PMID 29764978
    .
  14. PMID 20011543
    . 
11. Mol Cell. 2002 Jan;9(1):23-30. Hfq: a bacterial Sm-like protein that mediates RNA-RNA interaction.Møller T1, Franch T,    Højrup P, Keene DR, Bächinger HP, Brennan RG, Valentin-Hansen P.
 
12. EMBO J. 2002 Jul 1;21(13):3546-56.Structures of the pleiotropic translational regulator Hfq and an Hfq-RNA complex: a bacterial Sm-like protein. Schumacher MA1, Pearson RF, Møller T, Valentin-Hansen P, Brennan RG.

External links
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