Primary Citation of Related Structures: 5ER7, 5ERA
PubMed 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+) ...
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.
Related Citations:
Steroid-based facial amphiphiles for stabilization and crystallization of membrane proteins. Lee, S.C., Bennett, B.C., Hong, W.X., Fu, Y., Baker, K.A., Marcoux, J., Robinson, C.V., Ward, A.B., Halpert, J.R., Stevens, R.C., Stout, C.D., Yeager, M.J., Zhang, Q. (2013) Proc Natl Acad Sci U S A 110: E1203
Organizational Affiliation:
Department of Medicine, Division of Cardiovascular Medicine, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
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