The Helicobacter pylori neutrophil-activating protein is an iron-binding protein with dodecameric structure

Mol Microbiol. 1999 Oct;34(2):238-46. doi: 10.1046/j.1365-2958.1999.01584.x.


The neutrophil-activating protein (HP-NAP) of Helicobacter pylori is a major 17 kDa antigen of the immune response of infected individuals. Amino acid sequence comparison indicated a high similarity between HP-NAP and both bacterial DNA-protecting proteins (Dps) and ferritins. The structure prediction and spectroscopic analysis presented here indicate a close similarity between HP-NAP and Dps. Electron microscopy revealed that HP-NAP forms hexagonal rings of 9-10 nm diameter with a hollow central core as seen in Dps proteins, clearly different from the 12 nm icositetrameric (24 subunits) ferritins. However, HP-NAP is resistant to thermal and chemical denaturation similar to the ferritin family of proteins. In addition, HP-NAP binds up to 40 atoms of iron per monomer and does not bind DNA. We therefore conclude that HP-NAP is an unusual, small, ferritin that folds into a four-helix bundle that oligomerizes into dodecamers with a central hole capable of binding up to 500 iron atoms per oligomer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism*
  • Circular Dichroism
  • DNA / metabolism
  • Helicobacter pylori / chemistry*
  • Helicobacter pylori / metabolism
  • Iron / metabolism*
  • Microscopy, Electron
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Conformation
  • Protein Denaturation
  • Spectrometry, Fluorescence


  • Bacterial Proteins
  • neutrophil-activating protein A, Helicobacter pylori
  • DNA
  • Iron