Substitution of lysine for arginine at position 42 of human transforming growth factor-alpha eliminates biological activity without changing internal disulfide bonds.
Transforming growth factor-alpha (TGF-alpha) is a growth-promoting protein that binds to the epidermal growth factor (EGF) receptor. To identify critical residues that govern TGF-alpha-EGF receptor binding, we prepared site-specific substitution mutants of TGF-alpha. Mutant proteins were tested in receptor-binding and mitogenesis assays. Semiconservative substitutions at positions 4, 12, 18, and 45 decreased biological activity 2.1- to 14-fold. The conservative substitution of lysine for arginine at position 42 completely eliminated biological activity. Amino acid composition analysis of proteolytic fragments from TGF-alpha and the Lys-42 mutant indicated that these proteins contained the same disulfide bonds. These studies suggest that arginine 42 may be a contact point for TGF-alpha-EGF receptor interaction.
Defeo-Jones
D
D
Department of Cancer Research, Merck Sharp and Dohme Research Laboratories, West Point, Pennsylvania 19486.
Tai
J Y
JY
Vuocolo
G A
GA
Wegrzyn
R J
RJ
Schofield
T L
TL
Riemen
M W
MW
Oliff
A
A
D000595:Amino Acid Sequence; D001120:Arginine; D001665:Binding Sites; D004220:Disulfides; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D008239:Lysine; D008934:Mitogens; D008969:Molecular Sequence Data; D015291:Transforming Growth Factors / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology
D004220:Disulfides; D008934:Mitogens; D015291:Transforming Growth Factors; D001120:Arginine; D066246:ErbB Receptors; D008239:Lysine