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Article
Subject Categories: Membranes & Transport | Signal Transduction
The EMBO Journal (2003) 22, 826–832, doi:10.1093/emboj/cdg095
Galphas is palmitoylated at the N-terminal glycine
Christiane Kleuss1 and Eberhard Krause2
1 Institut für Pharmakologie, Freie Universität Berlin, Thielallee 67–73, 14195 Berlin Germany
2 Forschungsinstitut für Molekulare Pharmakologie, Campus Berlin Buch, Robert-Rössle-Strasse 10, 13125 Berlin-Buch, Germany

To whom correspondence should be addressed
Christiane Kleuss, ckleuss@zedat.fu-berlin.de

Received 21 October 2002; Revised 17 December 2002; Accepted 23 December 2002.
Abstract
Covalent lipid attachments are essential co- and post-translational modifications for signalling proteins. Galphas, the alpha-subunit of the heterotrimeric G protein that activates adenylyl cyclase, is known to be palmitoylated at the third N-terminal amino acid, a cysteine. Palmitoylation is involved in anchoring Galphas to the membrane by increasing its intrinsic hydrophobicity. We identified by mass spectrometry a second, functionally even more important, covalent modification. It consists of another palmitoyl residue attached to the preceding glycine (Gly2). Palmitoylation at this position has profound consequences for levels of signal transduction. It sensitizes the cell up to 200-fold for adenylyl cyclase-stimulating agents. The inhibitory inputs mediated by Galphai are downregulated to <10%. Thereby, Gly2-palmitoylation of Galphas relieves cellular stimulation at the level of adenylyl cyclase whereas it renders the inhibitory modulation via Galphai more difficult.
Keywords: adenylyl cyclase, Gly2-palmitoylation, lipid modification, stimulatory G protein
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