The domain structure of the ion channel-forming protein colicin Ia.
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.
Ghosh
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P
Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448, USA.
Mel
S F
SF
Stroud
R M
RM
D002462:Cell Membrane / Q000737:chemistry; D003087:Colicins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D007473:Ion Channels / Q000737:chemistry*; D011487:Protein Conformation
D003087:Colicins; D007473:Ion Channels