title: Galphas protein C-terminal alpha-helix at the interface: does the plasma membrane play a critical role in the Galphas protein functionality?
abstract: The heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins, Galphabetagamma) mediate the signalling process of a large number of receptors, known as G protein-coupled receptors. The C-terminal domain of the heterotrimeric G protein alpha-subunit plays a key role in the selective activation of G proteins by their cognate receptors. The interaction of this domain can take place at the end of a cascade including several successive conformational modifications. Galpha(s)(350-394) is the 45-mer peptide corresponding to the C-terminal region of the Galpha(s) subunit. In the crystal structure of the Galpha(s) subunit it encompasses the alpha4/beta6 loop, the beta6 beta-sheet segment and the alpha5 helix region. Following a previous study based on the synthesis, biological activity and conformational analysis of shorter peptides belonging to the same Galpha(s) region, Galpha(s)(350-394) was synthesized and investigated. The present study outlines the central role played by the residues involved in the alpha4/beta6 loop and beta6/alpha5 loops in the stabilization of the C-terminal Galpha(s)alpha-helix. H(2)O/(2)H(2)O exchange experiments, and NMR diffusion experiments show interesting evidence concerning the interaction between the SDS micelles and the polypeptide. These data prompt intriguing speculations on the role of the intracellular environment/cellular membrane interface in the stabilization and functionality of the C-terminal Galpha(s) region.
authors.affiliation: Dipartimento di Chimica Farmaceutica e Tossicologica, Università di Napoli Federico II, 80131 Napoli, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Albrizio
authors.forename: Gabriella
authors.initials: G
authors.lastname: Caliendo
authors.forename: Gerardino
authors.initials: G
authors.lastname: D'Errico
authors.forename: Ettore
authors.initials: E
authors.lastname: Novellino
authors.forename: Paolo
authors.initials: P
authors.lastname: Rovero
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: D'Ursi
mesh_terms: D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000378:metabolism*; D003903:Deuterium; D004058:Diffusion; D004578:Electron Spin Resonance Spectroscopy; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000737:chemistry* / Q000378:metabolism*; D008823:Micelles; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D017434:Protein Structure, Tertiary; D012967:Sodium Dodecyl Sulfate
chemical_list: D008823:Micelles; D012967:Sodium Dodecyl Sulfate; D003903:Deuterium; D019205:GTP-Binding Protein alpha Subunits, Gs