Protein Family Models

The phage-encoded excisionase protein Tn916-Xis adopts a winged-helix structure that consists of a three-stranded anti-parallel beta-sheet that packs against a helix-turn-helix (HTH) motif and a third C-terminal alpha-helix. It is encoded for by Tn916, which also codes for the integrase Tn916-Int. The protein interacts with DNA by the insertion of helix alpha-2 into the major groove and the contact of the hairpin that connects strands beta-2 and beta-3 with the adjacent phosphodiester backbone and/or minor groove. Tn916-Xis stimulates phage excision and inhibits viral integration by stabilising distorted DNA structures [1]. [1]. 15733914. The structure of the excisionase (Xis) protein from conjugative transposon Tn916 provides insights into the regulation of heterobivalent tyrosine recombinases. Abbani M, Iwahara M, Clubb RT;. J Mol Biol. 2005;347:11-25. (from Pfam)

Date:

2024-10-16

An excisionase, or Xis protein, is a small protein that binds and promotes excisive recombination; it is not enzymatically active. This HMM represents a number of putative excisionases and related proteins from temperate phage, plasmids, and transposons, as well as DNA binding domains of other proteins, such as a DNA modification methylase. This HMM identifies mostly small proteins and N-terminal regions of large proteins, but some proteins appear to have two copies. This domain appears similar, in both sequence and predicted secondary structure (PSIPRED) to the MerR family of transcriptional regulators (PF00376).

Date:

2021-04-27