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Two intracellular helices of G‐protein coupling receptors as transducer‐attaching entities
Author(s) -
Parker Steven L,
Parker Michael S
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.771.1
Subject(s) - g protein , intracellular , pertussis toxin , biophysics , protein subunit , microbiology and biotechnology , receptor , helix (gastropod) , gtpase , phosphorylation , biology , chemistry , biochemistry , ecology , snail , gene
The C‐terminal tract in the third intracellular (ic3) domain, and the juxtamembrane tract in the fourth intracellular (ic4) domain of G‐protein coupling receptors are known to interact with G‐proteins. Both segments show considerable conservation of sequence and size. These tracts have 12–17 residues, large content of basic sidechains, and high potential helicity. This is found regardless of domain size (which can exceed 400 residues), or the preferred G‐protein alpha subunit, and should represent a designated ability to interact with transducers. Association of either tract with transducers could be enhanced by restricted mobility (due to interaction with the bilayer) and broadside orientation, and could involve especially the long C‐terminal anion sidechain‐rich stretches in G‐protein subunits. Both tracts also show little phosphorylation compared to the rest of their domains, indicating a low processing by kinases and phosphatases, and low involvement in disassembly of transductional complexes. Helix 8 could perform as primary G‐protein partner, in the stable precoupling of receptors and G‐proteins as well as in GTPase activation upon agonist attachment. This is evidenced by effect of pertussis toxin on receptor/G‐protein heteropentamers. The ic3 C‐terminal helix could assist G‐protein coupling, and is widely known to perform in transducer activation.