TY - JOUR
T1 - Covalent binding of arachidonate to G protein α subunits of human platelets
AU - Hallak, Hazem
AU - Muszbek, Laszlo
AU - Laposata, Michael
AU - Belmonte, Elizabeth
AU - Brass, Lawrence F.
AU - Manning, David R.
N1 - Copyright:
Copyright 2014 Elsevier B.V., All rights reserved.
PY - 1994/2/18
Y1 - 1994/2/18
N2 - The α subunits of GTP-binding regulatory proteins (G proteins) are subject to lipid modifications required for anchorage to membrane and/or interactions with other proteins. With the knowledge that α subunits are palmitoylated, which we demonstrate here for human platelets, we sought to determine whether these subunits also bind arachidonate and myristate in a covalent, post-translational manner. All α subunits examined were found to incorporate radioactivity upon incubation of human platelets with [3H]palmitate, [3H]arachidonate, and [3H]myristate. The identity of [3H]palmitate and [3H]arachidonate as covalently bound fatty acids was confirmed by high pressure liquid chromatography following alkaline methanolysis. With [3H]myristate, however, the bound fatty acid proved to be [3H]palmitate, presumably generated by a 2-carbon chain elongation. Protein- bound [3H]palmitate and [3H]arachidonate were released by hydroxylamine at neutral pH, implying a thioester linkage between protein and fatty acid. Thus, post-translational modifications of G protein α subunits include palmitoylation and arachidonoylation, but not myristoylation. Given the different physical properties of saturated and unsaturated fatty acids and the large-scale release of arachidonate during platelet activation, changes in arachidonate incorporation may serve as an important regulator of α subunit function.
AB - The α subunits of GTP-binding regulatory proteins (G proteins) are subject to lipid modifications required for anchorage to membrane and/or interactions with other proteins. With the knowledge that α subunits are palmitoylated, which we demonstrate here for human platelets, we sought to determine whether these subunits also bind arachidonate and myristate in a covalent, post-translational manner. All α subunits examined were found to incorporate radioactivity upon incubation of human platelets with [3H]palmitate, [3H]arachidonate, and [3H]myristate. The identity of [3H]palmitate and [3H]arachidonate as covalently bound fatty acids was confirmed by high pressure liquid chromatography following alkaline methanolysis. With [3H]myristate, however, the bound fatty acid proved to be [3H]palmitate, presumably generated by a 2-carbon chain elongation. Protein- bound [3H]palmitate and [3H]arachidonate were released by hydroxylamine at neutral pH, implying a thioester linkage between protein and fatty acid. Thus, post-translational modifications of G protein α subunits include palmitoylation and arachidonoylation, but not myristoylation. Given the different physical properties of saturated and unsaturated fatty acids and the large-scale release of arachidonate during platelet activation, changes in arachidonate incorporation may serve as an important regulator of α subunit function.
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M3 - Article
C2 - 8106438
AN - SCOPUS:0028041579
SN - 0021-9258
VL - 269
SP - 4713
EP - 4716
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 7
ER -