Background: Transmembrane domain interactions in gap junction channels are poorly understood. Results: Tryptophan substitution experiments involving all four TM domains of Cx32 revealed tight packing. Conclusion: After modeling, tight packing was found to occur in the midregion. Pore-facing residues were highly sensitive to substitution, whereas lipid-facing residues were variably tolerant. Significance: Connexin-based channels are more densely packed than their innexin-based counterparts.
Through cysteine-scanning mutagenesis, the authors have compared sites within the transmembrane domains of two connexins, one from the α-class (Cx50) and one from the β-class (Cx32), where amino acid substitution disrupts the function of gap junction channels. In Cx32, 11 sites resulted in no channel function, or an aberrant voltage gating phenotype referred to as "reverse gating," whereas in Cx50, 7 such sites were identified. In both connexins, the sites lie along specific faces of transmembrane helices, suggesting that these may be sites of transmembrane domain interactions. In Cx32, one broad face of the M1 transmembrane domain and a narrower, polar face of M3 were identified, including one site that was shown to come into close apposition with M4 in the closed state. In Cx50, the same face of M3 was identified, but sensitive sites in M1 differed from Cx32. Many fewer sites in M1 disrupted channel function in Cx50, and those that did were on a different helical face to the sensitive sites in Cx32. A more in depth study of two sites in M1 and M2 of Cx32 showed that side-chain length or branching are important for maintenance of normal channel behavior, consistent with this being a site of transmembrane domain interaction.
architecture of Cx26. Results obtained from our simulations show that the studied mutations modify the position of the constriction zone in the hemmi-chanel, change the diameter of the pore and produce rearragements on the electrostatic potential inside the channel. These changes are related to an increase on the freedom of movement of the N-terminal helix and trans-membrane helix 1 (TM1) of each sub-unit. These results provide relevant clues and insights about the effect of these mutations over the hemi-channel perm-selectivity and conductance.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.