MOLECULAR-CLONING OF A GTPASE ACTIVATING PROTEIN-SPECIFIC FOR THE KREV-1 PROTEIN P21RAP1

The rap1/Krev-1 gene encodes a ras-related protein that suppresses transformation by ras oncogenes. We have purified an 88 kd GTPase activating protein (GAP), specific for the rap1/Krev-1 gene product, from bovine brain. Based on partial amino acid sequences obtained from this protein, a 3.3 kb cDNA was isolated f rom a human brain library. Expression of the cDNA in insect Sf9 cells resulted in high level production of an 85-95 kd rap1GAP that specifically stimulated the GTPase activity of p2l(rap1). The complete deduced amino acid sequence is not homologous to any known protein sequences, including GAPs specific for p2l(ras). Northern and Western blotting analysis indicate that raplGAP is not ubiquitously expressed and appears most abundant in fetal tissues and certain tumor cell lines, particularly the Wilms' kidney tumor, SK-NEP-1, and the melanoma, SK-MEL-3, cell lines.