title: The domain structure of the ion channel-forming protein colicin Ia.
abstract: Colicin Ia undergoes a transition from a soluble to a transmembrane state, forming an ion channel to effect its bactericidal activity. The X-ray crystal structure of soluble colicin Ia at an effective resolution of 4 A reveals that the molecule is highly alpha-helical and has an unusually elongated 'Y'-shape. The stalk and two arms of the 'Y' form three discrete structural domains which most likely correspond to the three functional regions identified for the channel-forming colicins. The channel-forming region of colicin Ia can be located to the larger of the two arms, the insertion domain, by its structural similarity to the ten alpha-helix motif found for the ion channel-forming fragments of colicins A and E1. The domain arrangement found in this structure provides novel insights into the mechanism of membrane insertion of colicin Ia.
authors.affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448, USA.
authors.forename: P
authors.initials: P
authors.lastname: Ghosh
authors.forename: S F
authors.initials: SF
authors.lastname: Mel
authors.forename: R M
authors.initials: RM
authors.lastname: Stroud
mesh_terms: D002462:Cell Membrane / Q000737:chemistry; D003087:Colicins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D007473:Ion Channels / Q000737:chemistry*; D011487:Protein Conformation
chemical_list: D003087:Colicins; D007473:Ion Channels