Structure function relations of gap junctions

We are investigating the structure-function relationships of voltage dependent gap junctions encoded by the vertebrate connexin gene family. Recently we have identified several amino acid residues that formpart of the transjunctional voltage sensor in two closely related members of the connexin gene family; Cx26 and Cx32 and have identified amino acid residues that form the physical gate of a second gating mechanism termed loop-gating. We are further examining the structural implications and operation of voltage dependent gating by site directed mutagenesis, expression of in vitro synthesized RNA in Xenopus oocytes, Molecular Dynamics simulations of connexin hemichannels imbedded into model membranes and with the solution structure of peptides with NMR. A major objective of our recent work is the creation of models of voltage-gated closed state and their validation. Atomic models of open and closed states allows the use of computational methods to describe the transition pathway. We are extending the results obtained from our investigations of Cx26 and Cx32 to other, more distantly related members of the connexin gene family to determine the generality of the gating mechanisms we have described.<

Abrams, C.K., Islam, M. Mahmoud, R., Kwon, T., Bargiello, T.A., and Freidin, M.M. (2013). Functional Requirement for a Highly Conserved Charged Residue at Position 75 in the Gap Junction Protein Connexin 32. J. Biol Chem. 288:3609–3619.

Kwon, T. Tang, Q, and Bargiello, T.A. (2013). Voltage-dependent gating of the Cx32*43E1 hemichannel: Conformational changes at the channel entrances. J. Gen Physiol. 141:243–259.

Kwon, T. Dowd, T.L., and Bargiello, T.A. (2013). The Carboxyl Terminal Residues 220–283 are not required for voltage gating of a chimeric Connexin32 hemichannel. Biophysical J. 105:1376–1382.

Kwon, T., Roux, B., Jo, S., Klauda, J. Harris, A.L. and Bargiello, T. A. (2012)Molecular Dynamics Simulations of the Cx26 Hemichannel: Insights into the mechanism of voltage-dependent loop-gating. Biophysical J. 102:1341–51.

Kalmatsky, B.D., Batir, Y., Bargiello, T.A. and Dowd, T.L. (2012) Structural Studies of N-terminus of Connexin 32 Using 1HNMR Spectroscopy. Arch. Biochem. Biophys. 526:1-8.

Bargiello, T.A., Tang, Q, Oh, S. and Kwon, T. (2012) Voltage-dependent Conformational Changes in Connexin Channels. Biochim. Biophys. Acta. 1818:1807–1822.

Kwon, T., Harris, A.L. Rossi, A and Bargiello, T.A. (2011) Molecular Dynamics Simulations of the Cx26 Hemichannel: Evaluation of structural models with Brownian Dynamics. J. Gen Physiol. 138:475–493.

Verselis V.K., Trelles M.P., Rubinos C, Bargiello T.A., and Srinivas M. (2009) Loop gating of connexin hemichannels involves a movement of pore-lining residues in the first extracellular domain. J Biol Chem. 284:4484–4493.

Freidin M, Asche S, Bargiello T.A., Bennett M.V., Abrams C.K. (2009) Connexin 32 increases the proliferative response of Schwann cells to neuregulin-1 (Nrg1). Proc Natl Acad Sci USA. 106:3567–72.

Tang, Q., Dowd, T.L., Verselis, V.K. and Bargiello, T.A. (2009) Conformational changes in a pore forming region underlie voltage dependent loop-gating of an unapposed connexin hemichannel. J Gen Physiol. 133:555–570.

Kalmatsky, B.D., Bhagan, S., Tang, Q, Bargiello, T.A., and Dowd, T.L. (2009) Structural Studies of the N-terminus of Connexin 32 Using 1H NMR Spectroscopy. Arch. Biochem. Biophys. 490:9–16.