PROSITE documentation PDOC51148
AXH domain profile


The AXH (ataxin-1 and HMG-box protein 1) domain is a module of ~130 amino acids, which has been identified in ATX1 and in the apparently unrelated transcription factor HBP1 [1]. It is found in many vertebrate and invertebrate proteins. It has been suggested that the AXH domain is a molecular scaffold domain engaged in multiple protein-protein interactions and in RNA binding.

The AXH domain consists of a noncanonical oligonucleotide and oligosaccharide binding (OB) fold. Although sharing a similar OB fold, the structure of the AXH domains from ATX1 (see <PDB:1OA8>) and HBP1 (see <PDB:1V06>) have genuinely distinct folds. The differences are not, as in other chameleon sequences, determined by a different tendency to adopt distinct secondary structures: the two folds share the same secondary structure elements, but these are differently arranged in space. The AXH domain has a chameleon structure in which the N and C termini can adopt distinctly different conformation. Neither of the differences are induced by binding to another molecule. While clearly correlated (sharing a sequence identity of ca. 30% and a homology of ca. 50% depending on the species), AXH has slightly different domain boundaries and distinct properties in ATX1 and HBP1. There is a cluster of charged residues that could constitute a ligand-binding site [2,3].

Some proteins known to contain a AXH domain are listed below:

  • Animal ataxin-1 (ATX1), a neurodegenerative disorder protein whose glutamine-repeat expanded form causes spinocerebellar ataxia type 1 (SCA1) in humans and exerts cytotoxicity in Drosophila and mouse.
  • Animal Brother of ataxin-1 (Boat) [4].
  • Vetebrate HMG box containing protein 1 (HBP1). It is thought to be involved in an architectural regulation of chromatin and in specific gene expression.

The profile we developed covers the entire AXH domain.

Last update:

October 2005 / First entry.


Technical section

PROSITE method (with tools and information) covered by this documentation:

AXH, PS51148; AXH domain profile  (MATRIX)


1Authorsde Chiara C. Giannini C. Adinolfi S. de Boer J. Guida S. Ramos A. Jodice C. Kioussis D. Pastore A.
TitleThe AXH module: an independently folded domain common to ataxin-1 and HBP1.
SourceFEBS Lett. 551:107-112(2003).
PubMed ID12965213

2AuthorsChen Y.W. Allen M.D. Veprintsev D.B. Loewe J. Bycroft M.
TitleThe structure of the AXH domain of spinocerebellar ataxin-1.
SourceJ. Biol. Chem. 279:3758-3765(2004).
PubMed ID14583607

3Authorsde Chiara C. Menon R.P. Adinolfi S. de Boer J. Ktistaki E. Kelly G. Calder L. Kioussis D. Pastore A.
TitleThe AXH domain adopts alternative folds the solution structure of HBP1 AXH.
SourceStructure 13:743-753(2005).
PubMed ID15893665

4AuthorsMizutani A. Wang L. Rajan H. Vig P.J.S. Alaynick W.A. Thaler J.P.
TitleTsai C.-C. Boat, an AXH domain protein, suppresses the cytotoxicity of mutant ataxin-1.
SourceEMBO J. 24:3339-3351(2005).
PubMed ID16121196

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