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Biophys. J. BioFAST: First Published October 7, 2005. doi:10.1529/biophysj.105.066373
© 2005 by the Biophysical Society.

A more recent version of this article appeared on January 1, 2006.
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CHANNELS, RECEPTORS, AND ELECTRICAL SIGNALING

Conductance of connexin hemichannels segregates with the first transmembrane segment

Xinge Hu 1, Meiyun Ma 1 and Gerhard Dahl 1*

1 University of Miami

* To whom correspondence should be addressed. E-mail: gdahl{at}miami.edu.

Submitted on May 11, 2005
Revised on June 3, 2005
Accepted on 13 September 2005


  Abstract
Gap junction channels are intercellular channels that mediate the gated transfer of molecules between adjacent cells. To identify the domain determining channel conductance, the first transmembrane segment (M1) was reciprocally exchanged between Cx46 and Cx32E143. The resulting chimeras exhibited conductances similar to that of the respective M1 donor. Furthermore, a chimera with the carboxy-terminal half of M1 in Cx46 replaced by that of Cx32 exhibited a conductance similar to that of Cx32E143, while the chimera with only the amino-terminal half of M1 replaced retained the unitary conductance of wild type Cx46. Extending the M1 domain swapping to other connexins by replacing the carboxyterminal half of M1 in Cx46 with that of Cx37 yielded a chimera channel with increased unitary conductance close to that of Cx37. Furthermore, a point mutant of Cx46, with leucine substituted by glycine in position 35, displayed a conductance much larger than that of the wild type. Thus, the M1 segment, especially the second half, contains important determinants of conductance of the connexin channel.

Key Words: channel, connexin, patch clamp, pore, spermine, unitary conductance




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Copyright © 2005 by the Biophysical Society.