title: An electrostatic mechanism for Ca(2+)-mediated regulation of gap junction channels.
abstract: Gap junction channels mediate intercellular signalling that is crucial in tissue development, homeostasis and pathologic states such as cardiac arrhythmias, cancer and trauma. To explore the mechanism by which Ca(2+) blocks intercellular communication during tissue injury, we determined the X-ray crystal structures of the human Cx26 gap junction channel with and without bound Ca(2+). The two structures were nearly identical, ruling out both a large-scale structural change and a local steric constriction of the pore. Ca(2+) coordination sites reside at the interfaces between adjacent subunits, near the entrance to the extracellular gap, where local, side chain conformational rearrangements enable Ca(2+)chelation. Computational analysis revealed that Ca(2+)-binding generates a positive electrostatic barrier that substantially inhibits permeation of cations such as K(+) into the pore. Our results provide structural evidence for a unique mechanism of channel regulation: ionic conduction block via an electrostatic barrier rather than steric occlusion of the channel pore.
authors.affiliation: Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
authors.forename: Brad C
authors.initials: BC
authors.lastname: Bennett
authors.affiliation: Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Purdy
authors.affiliation: Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: Kent A
authors.initials: KA
authors.lastname: Baker
authors.affiliation: Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California at San Diego, La Jolla, California 92093, USA.
authors.forename: Chayan
authors.initials: C
authors.lastname: Acharya
authors.affiliation: Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
authors.forename: William E
authors.initials: WE
authors.lastname: McIntire
authors.affiliation: Departments of Biological Sciences and Chemistry, Bridge Institute, University of Southern California, Los Angeles, California 90089, USA.
authors.forename: Raymond C
authors.initials: RC
authors.lastname: Stevens
authors.affiliation: Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: Qinghai
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology, Physiology and Neuroscience, Rutgers New Jersey Medical School, Newark, New Jersey 07103, USA.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Harris
authors.affiliation: Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California at San Diego, La Jolla, California 92093, USA.
authors.forename: Ruben
authors.initials: R
authors.lastname: Abagyan
authors.affiliation: Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.|Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.|Center for Membrane Biology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.|Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.|Department of Medicine, Division of Cardiovascular Medicine, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Yeager
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000072259:Connexin 26; D017630:Connexins / Q000737:chemistry / Q000378:metabolism*; D003460:Crystallization; D018360:Crystallography, X-Ray; D006801:Humans; D056004:Molecular Dynamics Simulation; D017434:Protein Structure, Tertiary; D061987:Sf9 Cells; D018411:Spodoptera; D055672:Static Electricity; D017356:Synchrotrons
chemical_list: D017630:Connexins; C000607042:GJB2 protein, human; D000072259:Connexin 26; D002118:Calcium