title: Structural changes in the carboxyl terminus of the gap junction protein connexin43 indicates signaling between binding domains for c-Src and zonula occludens-1.
abstract: Regulation of cell-cell communication by the gap junction protein connexin43 can be modulated by a variety of connexin-associating proteins. In particular, c-Src can disrupt the connexin43 (Cx43)-zonula occludens-1 (ZO-1) interaction, leading to down-regulation of gap junction intercellular communication. The binding sites for ZO-1 and c-Src correspond to widely separated Cx43 domains (approximately 100 residues apart); however, little is known about the structural modifications that may allow information to be transferred over this distance. Here, we have characterized the structure of the connexin43 carboxyl-terminal domain (Cx43CT) to assess its ability to interact with domains from ZO-1 and c-Src. NMR data indicate that the Cx43CT exists primarily as an elongated random coil, with two regions of alpha-helical structure. NMR titration experiments determined that the ZO-1 PDZ-2 domain affected the last 19 Cx43CT residues, a region larger than that reported to be required for Cx43CT-ZO-1 binding. The c-Src SH3 domain affected Cx43CT residues Lys-264-Lys-287, Ser-306-Glu-316, His-331-Phe-337, Leu-356-Val-359, and Ala-367-Ser-372. Only region Lys-264-Lys-287 contains the residues previously reported to act as an SH3 binding domain. The specificity of these interactions was verified by peptide competition experiments. Finally, we demonstrated that the SH3 domain could partially displace the Cx43CT-PDZ-2 complex. These studies represent the first structural characterization of a connexin domain when integrated in a multimolecular complex. Furthermore, we demonstrate that the structural characteristics of a disordered Cx43CT are advantageous for signaling between different binding partners that may be important in describing the mechanism of channel closure or internalization in response to pathophysiological stimuli.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA. psorgen@unmc.edu
authors.forename: Paul L
authors.initials: PL
authors.lastname: Sorgen
authors.forename: Heather S
authors.initials: HS
authors.lastname: Duffy
authors.forename: Prangya
authors.initials: P
authors.lastname: Sahoo
authors.forename: Wanda
authors.initials: W
authors.lastname: Coombs
authors.forename: Mario
authors.initials: M
authors.lastname: Delmar
authors.forename: David C
authors.initials: DC
authors.lastname: Spray
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D000081247:CSK Tyrosine-Protein Kinase; D018031:Connexin 43 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005982:Glutathione Transferase / Q000235:genetics; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D013438:Sulfhydryl Compounds / Q000378:metabolism; D062826:Zonula Occludens-1 Protein; D019061:src-Family Kinases
chemical_list: D018031:Connexin 43; D008565:Membrane Proteins; D010446:Peptide Fragments; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D013438:Sulfhydryl Compounds; D062826:Zonula Occludens-1 Protein; D005982:Glutathione Transferase; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases