This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.106.082859v1 91/6/2142    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Tong, J.-J. Articles by Ebihara, L. Search for Related Content PubMed PubMed Citation Articles by Tong, J.-J. Articles by Ebihara, L.

Structural Determinants for the Differences in Voltage Gating of Chicken Cx56 and Cx45.6 Gap-Junctional Hemichannels

Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064

Correspondence: Address reprint requests to Lisa Ebihara, Dept. of Physiology and Biophysics, Rosalind Franklin School of Medicine and Science/Chicago Medical School, 3333 Green Bay Rd. North, Chicago, IL 60064. Tel.: 847-578-3424; Fax: 847-578-3265; E-mail: lisa.ebihara{at}rosalindfranklin.edu.

The voltage- and calcium-dependent gating properties of two lens gap-junctional hemichannels were compared at the macroscopic and single channel level. In solutions containing zero added calcium and 1 mM Mg, chicken Cx56 hemichannels were mostly closed at negative potentials and application of depolarizing voltage clamp steps elicited a slowly activating outward current. In contrast, chicken Cx45.6 hemichannels were predominantly open at negative potentials and rapidly closed in response to application of large depolarizing potentials. Another difference was that macroscopic Cx45.6 currents were much smaller in size than the hemichannel currents induced by oocytes with similar amounts of cRNA for Cx56. The aim of this study was to identify which regions of the connexins were responsible for the differences in voltage-dependent gating and macroscopic current amplitude by constructing a series of chimeric Cx45.6-Cx56 channels. Our results show that two charged amino acids that are specific for the 3-group connexins (R9 in the N-terminus and E43 in the first extracellular loop) are important determinants for the difference in voltage-dependent gating between Cx45.6 and Cx56 hemichannels; the first transmembrane-spanning domain, M1, is an important determinant of macroscopic current magnitude; R9 and E43 are also determinants of single channel conductance and rectification.

This article has been cited by other articles:

				B. C. Thomas, P. J. Minogue, V. Valiunas, G. Kanaporis, P. R. Brink, V. M. Berthoud, and E. C. Beyer Cataracts Are Caused by Alterations of a Critical N-Terminal Positive Charge in Connexin50 Invest. Ophthalmol. Vis. Sci., June 1, 2008; 49(6): 2549 - 2556. [Abstract] [Full Text] [PDF]

				D. Shearer, W. Ens, K. Standing, and G. Valdimarsson Posttranslational Modifications in Lens Fiber Connexins Identified by Off-Line-HPLC MALDI-Quadrupole Time-of-Flight Mass Spectrometry Invest. Ophthalmol. Vis. Sci., April 1, 2008; 49(4): 1553 - 1562. [Abstract] [Full Text] [PDF]