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Journal Articles Journal of Membrane Biology Year : 2004

Gating Movements of Colicin A and Colicin Ia Are Different

S.L. Slatin
  • Function : Author
P.K. Kienker
  • Function : Author
D. Baty
  • Function : Author


Both colicin A and colicin Ia belong to a subfamily of the bacterial colicins that act by forming a voltage-dependent channel in the inner membrane of target bacteria. Both colicin A and Ia open at positive and close at negative potential, but only colicin A exhibits distinctly biphasic turnoff kinetics, implying the existence of two open states. Previous work has shown that Colicin Ia gating is associated with the translocation of a region representing 4 of its alpha helices across the membrane. Also, if its C-terminal, channel-forming domain is detached from the other domains, its N-terminal alpha helix can now also cross the membrane, causing the conductance to drop by a factor of about 6. Colicin A gating also involves the translocation of an internal domain, but we find that its translocated domain is somewhat smaller than that of Ia. Furthermore, while its isolated C-terminal domain can also undergo a transition to a smaller conductance, the conductance change is only about 15%, and the transition does not involve the translocation of the N-terminal alpha helix. Trapping the N-terminus on the cis side prevents neither this small conductance transition nor the biphasic turn-off. So, while the gating of both channels involves large, currently inexplicable conformational changes, these motions are qualitatively different in the two proteins, which may be a reflection of the dissimilar kinetics of closing.

Dates and versions

hal-02894008 , version 1 (08-07-2020)



S.L. Slatin, Denis Duché, P.K. Kienker, D. Baty. Gating Movements of Colicin A and Colicin Ia Are Different. Journal of Membrane Biology, 2004, 202 (2), pp.73-83. ⟨10.1007/s00232-004-0720-9⟩. ⟨hal-02894008⟩
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