Subunit Structure of Islets-Activating Protein (IAP), a New Protein Isolated from the Culture Media of Bordetella pertussis

• Published in: Journal of biochemistry (Tokyo) 1978-08, Vol.84 (2), p.443-451
• Main Authors: KANBAYASHI, Yoshinori, NAKAMURA, Tsutomu, HOSODA, Koichi, NOGIMORI, Katsumi, YAJIMA, Motoyuki, UI, Michio
• Format: Article
• Language: English
• Subjects: Amino Acids - analysis; Animals; Bacterial Proteins - isolation & purification; Bordetella - analysis; Cell-Free System; Chemical Phenomena; Chemistry; Culture Media; Histamine H1 Antagonists; Hypoglycemic Agents; Islets of Langerhans - drug effects; Leukocytosis - chemically induced; Macromolecular Substances; Mice; Molecular Weight; Rats; Structure-Activity Relationship
• ISSN: 0021-924X; 1756-2651
• DOI: 10.1093/oxfordjournals.jbchem.a132145

The subunit structure was studied of islets-activating protein (IAP), a new protein recently isolated from the culture media of Bordetella pertussis and possessing a unique action, i.e., potentiating insulin secretory responses of animals, IAP dissociated into three subunits, F-l, F-2, and F-3, when incubated in 8 M urea. Three subunits isolated by chromatography on CM-Sepharose and DEAE-Sepharose columns showed different molecular weights (F-l: 44,000, F-2: 20,000, F-3: 11,000) and different isoelectric points, but similar amino acid compositions. The F-l subunit consisted of two polypeptide chains linked by S-S bonding(s), while the F-2 and F-3 subunits were single-chain peptides. These subunits, none of which was biologically active alone, associated upon incubation for 2 h at 37°C and regained biological activities after association only when the F-3 subunit was present in the association product. Thus, the F-3 subunit was essential, and the F-l and F-2 subunits were permissive, for the development of IAP activity in animals.