Igarashi T, Yokomizo T, Tsutsumi O, Taketani Y, Shimizu T, Izumi T. Characterization of the leukotriene B4 receptor in porcine leukocytes. Separation and reconstitution with heterotrimeric GTP-binding proteins.
EUROPEAN JOURNAL OF BIOCHEMISTRY 1999;
259:419-25. [PMID:
9914522 DOI:
10.1046/j.1432-1327.1999.00054.x]
[Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Leukotriene B4 (LTB4) is a potent chemoattractant derived from arachidonic acid. When cDNAs for LTB4 receptor (BLT) were cloned it was found that they belong to a guanine nucleotide-binding regulatory protein (G-protein)-coupled receptor superfamily. However, purification of BLT from inflammatory cells and reconstitution with various types of G-proteins have not been successful. In the present study, BLT from porcine leukocytes was solubilized, separated from associated G-proteins by Ricinus communis agglutinin (RCA) 120 chromatography, and reconstituted with several endogenous and exogenous G-proteins, in combination with the fraction which contained endogenous phospholipids and Gbeta gamma. Kinetic studies of LTB4 were performed to determine the association with G-proteins. A partially purified BLT fraction (retained on an RCA120 column) free of G-proteins showed a lower affinity for LTB4 (Kd = 500 nm), but reconstitution of the BLT fraction with a G-protein-rich fraction (flow-through of an RCA column) increased the affinity for LTB4 10-fold (Kd = 50 nm). The partially purified BLT fraction was also reconstituted with exogenous G-proteins such as a heterotrimeric Gi2 purified from bovine brain or recombinant alpha subunits of Gi1, Gi2, Gi3, and Go expressed in Spodoptera frugiperda-9 cells. These increases in LTB4 bindings demonstrate that the BLT of porcine leukocytes can interact with pertussis toxin-sensitive G-proteins in vitro. The method is useful for the purification and reconstitution of other, as yet unisolated, G-protein-coupled receptors.
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