DNA binding HTH domain, Fis-type (IPR002197)

Short name: HTH_Fis

Overlapping homologous superfamilies

Domain relationships



The Factor for Inversion Stimulation (FIS) protein is a regulator of bacterial functions, and binds specifically to weakly related DNA sequences [PMID: 7536730,PMID: 11123690]. It activates ribosomal RNA transcription, and is involved in upstream activation of rRNA promoters. The protein has been shown to play a role in the regulation of virulence factors in both Salmonella typhimurium and Escherichia coli [PMID: 11532124]. Some of its functions include inhibition of the initiation of DNA replication from the OriC site, and promotion of Hin-mediated DNA inversion.

In its C-terminal extremity, FIS encodes a helix-turn-helix (HTH) DNA- binding motif, which shares a high degree of similarity with other HTH motifs of more primitive bacterial transcriptional regulators, such as the nitrogen assimilation regulatory proteins (NtrC) from species like Azobacter, Rhodobacter and Rhizobium. This has led to speculation that both evolved from a single common ancestor [PMID: 9738943].

The 3-dimensional structure of the E. coli FIS DNA-binding protein has been determined by means of X-ray diffraction to 2.0A resolution [PMID: 1619650,PMID: 11183780]. FIS is composed of four alpha-helices tightly intertwined to form a globular dimer with two protruding HTH motifs. The 24 N-terminal amino acids are poorly defined, indicating that they might act as `feelers' suitable for DNA or protein (invertase) recognition [PMID: 1619650]. Other proteins belonging to this subfamily include:

  • E. coli: atoC, hydG, ntrC, fhlA, tyrR,
  • Rhizobium spp.: ntrC, nifA, dctD

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0043565 sequence-specific DNA binding

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.