Expression of a mutated bovine growth hormone gene suppresses growth of transgenic mice.
To determine the importance of the third alpha-helix in bovine growth hormone (bGH) relative to growth-related biological activities, the following experimental approach was used: (i) mutagenesis of helix III of bGH to generate an idealized amphiphilic helix; (ii) in vitro expression analyses of the mutated bGH gene in cultured mouse L cells; (iii) mouse liver membrane binding studies of wild-type and mutated bGH; and (iv) expression of the mutated gene in the transgenic mouse. An altered bGH gene (pBGH10 delta 6-M8) was generated that encodes the following changes: glutamate-117 to leucine, glycine-119 to arginine, and alanine-122 to aspartate. The plasmid pBGH10 delta 6-M8 was shown to be expressed in, and its protein product secreted by, mouse L cells. The altered hormone possessed the same binding affinity to mouse liver membrane preparations as wild-type bGH. Transgenic mice containing the mutated bGH gene, however, showed a significant growth-suppressed phenotype. The degree of suppression was directly related to serum levels of the altered bGH molecule.
Chen
W Y
WY
Department of Zoology, Ohio University, Athens 45701.
Wight
D C
DC
Wagner
T E
TE
Kopchick
J J
JJ
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002462:Cell Membrane; D005260:Female; D015870:Gene Expression; D005796:Genes; D013006:Growth Hormone / Q000235:genetics* / Q000502:physiology; D007700:Kinetics; D007739:L Cells / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D051379:Mice; D008822:Mice, Transgenic / Q000254:growth & development*; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids; D011487:Protein Conformation; D011986:Receptors, Somatotropin / Q000378:metabolism
D011986:Receptors, Somatotropin; D013006:Growth Hormone