Molecular characterization of CHAD domains as inorganic polyphosphate-binding modules

Life Sci Alliance. 2019 May 27;2(3):e201900385. doi: 10.26508/lsa.201900385. Print 2019 Jun.


Inorganic polyphosphates (polyPs) are linear polymers of orthophosphate units linked by phosphoanhydride bonds. Here, we report that bacterial, archaeal, and eukaryotic conserved histidine α-helical (CHAD) domains are specific polyP-binding modules. Crystal structures reveal that CHAD domains are formed by two four-helix bundles, giving rise to a central pore surrounded by conserved basic surface patches. Different CHAD domains bind polyPs with dissociation constants ranging from the nano- to mid-micromolar range, but not nucleic acids. A CHAD-polyP complex structure reveals the phosphate polymer binding across the central pore and along the two basic patches. Mutational analysis of CHAD-polyP interface residues validates the complex structure. The presence of a CHAD domain in the polyPase ygiF enhances its enzymatic activity. The only known CHAD protein from the plant Ricinus communis localizes to the nucleus/nucleolus when expressed in Arabidopsis and tobacco, suggesting that plants may harbor polyPs in these compartments. We propose that CHAD domains may be used to engineer the properties of polyP-metabolizing enzymes and to specifically localize polyP stores in eukaryotic cells and tissues.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Cell Line
  • Eukaryotic Cells*
  • Histidine
  • Models, Molecular*
  • Polyphosphates / chemistry*
  • Protein Binding
  • Protein Conformation
  • Protein Conformation, alpha-Helical
  • Protein Domains*
  • Protein Interaction Domains and Motifs*


  • Polyphosphates
  • Histidine

Associated data

  • PDB/3E0S
  • PDB/5A61
  • PDB/1U6Z
  • PDB/2QB7
  • PDB/5LLF
  • PDB/3G3Q
  • PDB/1XDP