Bovine peripheral neutrophils contain high levels of a 40‐kDa pertussis toxin substrate, which was found highly enriched in a light membrane fraction upon subcellular fractionation of neutrophil homogenates. The 40‐kDa pertussis toxin substrate, referred to as αn, was purified to near homogeneity from this fraction by sequential ion‐exchange, gel‐filtration and hydrophobic chromatography. Purified αn was shown to interact with βγ subunits, undergo ADP‐ribosylation by pertussis toxin, and bind guanine nucleotides with high affinity. The mobility of purified αn on SDS/polyacrylamide gels was intermediate between those of the α subunits of Gi and Go, purified from bovine brain, and slightly lower than the mobility of the α subunit of transducin (Gt). Several polyclonal antisera against the α subunits of bovine Gt and Go did not react with αn on immunoblots. CW 6, a polyclonal antiserum reactive against the bovine αi, reacted only minimally with αn. These results suggest that the major pertussis toxin substrate of bovine neutrophils, designated Gn, is structurally different from previously identified pertussis toxin substrates and may represent a novel guanine‐nucleotide‐binding protein.
|Number of pages
|European Journal of Biochemistry
|Published - May 1987
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