TABLE 1.

Retroviral vectors expressing the IGF-1 receptors used in these experiments^a

Vector	Mutation(s)
GR15	None (wild-type receptor)
GR18	Tyrosines 950, 1131, 1135, and 1136 to phenylalanines
GR25	Residues 1289, 1290, 1293, and 1294 to alanines
GR35	Serines at positions 1280 to 1283 to alanines
GR36	Truncated at residue 1245
GR46	Tyrosine 950 to phenylalanine
GR47	Residues 1293 and 1294 to alanines
GR48	Tyrosines 1131, 1135, and 1136 to alanines

^aThe following mutant vectors have been previously described in plasmids: GR35 (43), GR46 (52), GR36 and GR47 (30), and GR48 (42). The generation of the other mutants and their insertion into retroviruses have been described by Romano et al. (70).