Subunit structure of islets-activating protein (IAP), a new protein isolated from the culture media of Bordetella pertussis.
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-1, F-2, and F-3, when incubated in 8M urea. Three subunits isolated by chromatography on CM-Sepharose and DEAE-Sepharose columns showed different molecular weights (F-1: 44,000, F-2: 20,000, F-3: 11,000) and different isoelectric points, but similar amino acid compositions. The F-1 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 degrees 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-1 and F-2 subunits were permissive, for the development of IAP activity in animals.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001426:Bacterial Proteins / Q000302:isolation & purification*; D001884:Bordetella / Q000032:analysis*; D002474:Cell-Free System; D055598:Chemical Phenomena; D002621:Chemistry; D003470:Culture Media; D006634:Histamine H1 Antagonists; D007004:Hypoglycemic Agents; D007515:Islets of Langerhans / Q000187:drug effects*; D007964:Leukocytosis / Q000139:chemically induced; D046911:Macromolecular Substances; D051379:Mice; D008970:Molecular Weight; D051381:Rats; D013329:Structure-Activity Relationship
D000596:Amino Acids; D001426:Bacterial Proteins; D003470:Culture Media; D006634:Histamine H1 Antagonists; D007004:Hypoglycemic Agents; D046911:Macromolecular Substances