title: The Helicobacter pylori neutrophil-activating protein is an iron-binding protein with dodecameric structure.
abstract: 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.
authors.affiliation: Centro CNR Biomembrane and Dipartimento di Scienze Biomediche, Università di Padova, I-35121, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Tonello
authors.forename: W G
authors.initials: WG
authors.lastname: Dundon
authors.forename: B
authors.initials: B
authors.lastname: Satin
authors.forename: M
authors.initials: M
authors.lastname: Molinari
authors.forename: G
authors.initials: G
authors.lastname: Tognon
authors.forename: G
authors.initials: G
authors.lastname: Grandi
authors.forename: G
authors.initials: G
authors.lastname: Del Giudice
authors.forename: R
authors.initials: R
authors.lastname: Rappuoli
authors.forename: C
authors.initials: C
authors.lastname: Montecucco
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D002942:Circular Dichroism; D004247:DNA / Q000378:metabolism; D016480:Helicobacter pylori / Q000737:chemistry* / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D008854:Microscopy, Electron; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011489:Protein Denaturation; D013050:Spectrometry, Fluorescence
chemical_list: D001426:Bacterial Proteins; C092412:neutrophil-activating protein A, Helicobacter pylori; D004247:DNA; D007501:Iron