title: Identification of critical residues controlling G protein-gated inwardly rectifying K(+) channel activity through interactions with the beta gamma subunits of G proteins.
abstract: G protein-sensitive inwardly rectifying potassium (GIRK) channels are activated through direct interactions of their cytoplasmic N- and C-terminal domains with the beta gamma subunits of G proteins. By using a combination of biochemical and electrophysiological approaches, we identified minimal N- and C-terminal G beta gamma -binding domains responsible for stimulation of GIRK4 channel activity. Within these domains one N-terminal residue, His-64, and one C-terminal residue, Leu-268, proved critical for G beta gamma-mediated GIRK4 activity. Moreover, mutations at these GIRK4 sites reduced significantly binding of the channel domains to G beta gamma . The corresponding residues in GIRK1 also showed a critical involvement in G beta gamma sensitivity. In GIRK4/GIRK1 heteromers the GIRK4 His-64 and Leu-268 residues showed greater contributions to G beta zeta sensitivity than did the corresponding GIRK1 His-57 and Leu-262 residues. These results identify functionally important channel interaction sites with the beta gamma subunits of G proteins, critical for channel activity.
authors.affiliation: Department of Neurobiology, Second Military Medical University, Shanghai 200433, China. chnenghe@online.sh.cn
authors.forename: Cheng
authors.initials: C
authors.lastname: He
authors.forename: Xixin
authors.initials: X
authors.lastname: Yan
authors.forename: Hailin
authors.initials: H
authors.lastname: Zhang
authors.forename: Tooraj
authors.initials: T
authors.lastname: Mirshahi
authors.forename: Taihao
authors.initials: T
authors.lastname: Jin
authors.forename: Aijun
authors.initials: A
authors.lastname: Huang
authors.forename: Diomedes E
authors.initials: DE
authors.lastname: Logothetis
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D019204:GTP-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D007930:Leucine; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry* / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; C497066:KCNJ3 protein, human; D010446:Peptide Fragments; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D019204:GTP-Binding Proteins; D007930:Leucine