Biochemical and biological activities of N-ras proteins.

Recombinant N-ras proteins, expressed and produced from synthetic genes cloned into E. coli, have been tested in vitro for GTPase and autophosphorylation activity. The genes corresponding to the assayed proteins were tested for their ability to transform NIH 3T3 cells. Mutations of glutamine to lysine at amino acid position 61 and glycine to valine at position 12 were both found to activate the ability of the N-ras gene to transform NIH 3T3 cells while significantly reducing the GTPase activity of the corresponding protein. N-ras proteins were also found to autophosphorylate in the presence of GTP when a threonine acceptor amino acid is provided at position 59.