title: Secondary structural analysis of the carboxyl-terminal domain from different connexin isoforms.
abstract: The connexin carboxyl-terminal (CxCT) domain plays a role in the trafficking, localization, and turnover of gap junction channels, as well as the level of gap junction intercellular communication via numerous post-translational modifications and protein-protein interactions. As a key player in the regulation of gap junctions, the CT presents itself as a target for manipulation intended to modify function. Specific to intrinsically disordered proteins, identifying residues whose secondary structure can be manipulated will be critical toward unlocking the therapeutic potential of the CxCT domain. To accomplish this goal, we used biophysical methods to characterize CxCT domains attached to their fourth transmembrane domain (TM4). Circular dichroism and nuclear magnetic resonance were complementary in demonstrating the connexin isoforms that form the greatest amount of α-helical structure in their CT domain (Cx45 > Cx43 > Cx32 > Cx50 > Cx37 ≈ Cx40 ≈ Cx26). Studies compared the influence of 2,2,2-trifluoroethanol, pH, phosphorylation, and mutations (Cx32, X-linked Charcot-Marie Tooth disease; Cx26, hearing loss) on the TM4-CxCT structure. While pH modestly influences the CT structure, a major structural change was associated with phosphomimetic substitutions. Since most connexin CT domains are phosphorylated throughout their life cycle, studies of phospho-TM4-CxCT isoforms will be critical toward understanding the role that structure plays in regulating gap junction function.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198.
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Spagnol
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198.
authors.forename: Mona
authors.initials: M
authors.lastname: Al-Mugotir
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Kopanic
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198.
authors.forename: Sydney
authors.initials: S
authors.lastname: Zach
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198.
authors.forename: Hanjun
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Trease
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198.
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Stauch
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198.
authors.forename: Rosslyn
authors.initials: R
authors.lastname: Grosely
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198.
authors.forename: Matthew
authors.initials: M
authors.lastname: Cervantes
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198.
authors.forename: Paul L
authors.initials: PL
authors.lastname: Sorgen
mesh_terms: D002942:Circular Dichroism; D017630:Connexins / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D020033:Protein Isoforms / Q000737:chemistry*; D017433:Protein Structure, Secondary
chemical_list: D017630:Connexins; D020033:Protein Isoforms
keywords: circular dichroism; gap junctions; intrinsically disordered; nuclear magnetic resonance