Nanomechanics of hemichannel conformations: Connexin flexibility underlying channel opening and closing

Fei Liu, Fernando Terán Arce, Srinivasan Ramachandran, Ratnesh Lal

Research output: Contribution to journalArticlepeer-review

61 Scopus citations

Abstract

Gap junctional hemichannels mediate cell-extracellular communication. A hemichannel is made of six connexin (Cx) subunits; each connexin has four transmembrane domains, two extracellular loops, and cytoplasmic amino- and carboxyl-terminals (CTs). The extracellular domains are arranged differently at non-junctional and junctional (gap junction) regions, although very little is known about their flexibility and conformational energetics. The cytoplasmic tail differs considerably in the size and amino acid sequence for different connexins and is predicted to be involved in the channel open and closed conformations. For large connexins, such as Cx43, the CT makes large cytoplasmic fuzz visible under electron microscopy. If this CT domain controls channel permeability by physical occlusion of the pore mouth, movement of this portion could open or close the channel. We used atomic force microscopy-based single molecule spectroscopy with antibody-modified atomic force microscopy tips and connexin mimetic peptide modified tips to examine the flexibility of extracellular loop and CT domains and to estimate the energetics of their movements. Antibody to the CT portion closer to the membrane stretches the tail to a shorter length, and the antibody to CT tail stretches the tail to a longer length. The stretch length and the energy required for stretching the various portions of the carboxyl tail support the ball and chain model for hemichannel conformational changes.

Original languageEnglish (US)
Pages (from-to)23207-23217
Number of pages11
JournalJournal of Biological Chemistry
Volume281
Issue number32
DOIs
StatePublished - Aug 11 2006
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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