Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Three gap junctional proteins have been identified in canine ventricular myocytes: connexin 43 (Cx43), connexin 45 (Cx45), and connexin 40 (Cx40). We have characterized the functional properties of canine Cx45 and examined how Cx45 functionally interacts with Cx43 in Xenopus oocyte pairs. Homotypic pairs expressing Cx45 were well coupled. Heterotypic pairs composed of Cx45 paired with either Cx43 or Cx38 also developed high levels of conductance. Junctional currents in the heterotypic pairs displayed a highly asymmetrical voltage dependence. The kinetics and steadystate voltage dependence of the heterotypic channels more closely resembled those of the Cx45 channels when the Cx45 cRNA-injected cell was relatively negative suggesting that the Cx45 connexin closes for relative negativity at the cytoplasmic end of the channel. We also show that homotypic and heterotypic channels composed of Cx45 and Cx43 exhibit differences in pHi sensitivity.
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PMID:Functional characterization of canine connexin45. 866 73

Although fast and slow gating mechanisms have been described in gap junctions (GJs), their relative contributions to dependence on transjunctional voltage, V(j), is still unclear. We used cell lines expressing wild-type connexin 45 (Cx45) and connexin 43 fused with enhanced green fluorescent protein (Cx43-EGFP) to examine mechanisms of gating in homo- and heterotypic GJs formed of these connexins. Macroscopically Cx45/Cx45 channels show high sensitivity to V(j). Cx45 channels demonstrate two types of gating: fast transitions between open and residual states and slow transitions between open and completely closed states. Single-channel conductance of the Cx45 channel is approximately 32 pS for the open state and approximately 4 pS for the residual state. Cx45/Cx43-EGFP heterotypic junctions exhibit very asymmetrical V(j) gating with the maximum junctional conductance shifted to V(j) positive on the Cx45 side. Conductance of single Cx45/Cx43-EGFP channels is approximately 55 pS for the open state and approximately 4 pS for the residual state, values consistent with the simple-series connection of Cx45 and Cx43-EGFP hemichannels. At V(j) = 0, the slow gate of many Cx45 hemichannels is closed in both homotypic Cx45/Cx45 and heterotypic Cx45/Cx43-EGFP junctions. Fast and slow V(j) gates of both Cx45 and Cx43 hemichannels close for relative negativity at their cytoplasmic end. Coupling mediated by Cx45/Cx43-EGFP junctions can exhibit asymmetry that can be strongly modulated by small changes in difference of holding potentials. Cx45/Cx43 junctions are likely to be found in brain and heart and may mediate rectifying electrical transmission or modulatable chemical communication.
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PMID:Coupling asymmetry of heterotypic connexin 45/ connexin 43-EGFP gap junctions: properties of fast and slow gating mechanisms. 1201 67