Journal of Biological Chemistry
Volume 278, Issue 13, 28 March 2003, Pages 11237-11245
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MEMBRANE TRANSPORT STRUCTURE FUNCTION AND BIOGENESIS
C Termini of the Escherichia coli Mechanosensitive Ion Channel (MscS) Move Apart upon the Channel Opening*

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Heptameric YggB is a mechanosensitive ion channel (MscS) from the inner membrane of Escherichia coli. We demonstrate, using the patch clamp technique, that cross-linking of the YggB C termini led to irreversible inhibition of the channel activities. Application of Ni2+ to the YggB-His6 channels with the hexahistidine tags added to the ends of their C termini also resulted in a marked but reversible decrease of activities. Western blot revealed that YggB-His6 oligomers are more stable in the presence of Ni2+, providing evidence that Ni2+ is coordinated between C termini from different subunits of the channel. Intersubunit coordination of Ni2+ affecting channel activities occurred in the channel closed conformation and not in the open state. This may suggest that the C termini move apart upon channel opening and are involved in the channel activation. We propose that the as yet undefined C-terminal region may form a cytoplasmic gate of the channel. The results are discussed and interpreted based on the recently released quaternary structure of the channel.

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*

This work was supported by Grant KBN 6P04C 002 20 from the State Committee for Scientific Research and funding from the Nencki Institute of Experimental Biology.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Fellow of the Foundation for Polish Science.