Identification and purification of a novel G protein from neutrophils

Abstract

A novel G protein which appears to couple chemotactic peptide receptors to a polyphosphoinositide phospholipase C has been purified from rabbit neutrophils. Neutrophil membranes were solubilized with sodium cholate and fractionated by successive anion exchange, gel filtration and hydrophobic chromatography. Guanosine-5′-(3-O-thio)triphosphate binding activity was purified 170-fold from the soluble extract. The α-subunit of the purified G protein was identified by pertussis toxin-catalyzed ADP-ribosylation, and found to have an M _r of 40 000. The β-subunit (M _r 36 000) comigrated on SDS-polyacrylamide gel electrophoresis with the β-subunits of bovine brain Gi and Go. The neutrophil pertussis toxin substrate is highly unstable in cholate solution unless 30% ethylene glycol is added. Structural and functional analysis of this novel G protein will advance our understanding of the molecular mechanisms of coupling of receptors to phospholipase C.