Identification of novel GTP-binding proteins in the human neutrophil

We describe here the existence of previously undescribed GTP-binding proteins within the human neutrophil. These proteins specifically bind guanine nucleotides under conditions in which the previously characterized G-proteins are unable to bind. We have partially purified these proteins and present both functional and immunologic data which indicate that they are unrelated to Gn, the major neutrophil pertussis toxin substrate. An additional protein, of apparent molecular mass 22 kDa, may be related to the ras G-protein family. Analysis of the structural and functional characteristics of these novel proteins will promote a better understanding of the process of neutrophil activation.