Activity of artificial mutant variants of human growth hormone deficient in a disulfide bond between Cys53 and Cys165.
In order to understand the role of Cys53 and Cys165 of human growth hormone (hGH) in receptor-binding and biological activity, artificial mutant variants of hGH were prepared in Escherichia coli by in vitro mutagenesis. Variants of hGH were constructed by replacement of Cys165 with Ala ([Ala165]hGH) or Ser ([Ser165]hGH), by replacement of Cys53 with Ala ([Ala53]hGH), by replacement of Cys53 and Cys165 with Ala ([Ala53, Ala165]hGH), or by replacement of Cys53 with Ala and Cys165 with Ser ([Ala53,Ser165]hGH). All of the variants constructed as well as reduced hGH exhibited less biological activity than that of intact hGH, and the decreases in biological activity were almost equal, as measured by a sensitive biological assay for growth hormone: adipose conversion assay using 3T3-F442A cells. These variants also showed less receptor-binding activity than that of intact hGH. These results suggest that it is possible neither the residue Cys53 nor Cys165 is directly involved in the receptor binding, and that the disulfide bridge between Cys53 and Cys165 in hGH may not always be crucial for the biological activity, though necessary to express full hGH activity.
Uchida
E
E
Division of Biological Chemistry and Biologicals, National Institute of Hygienic Sciences, Tokyo, Japan.
Uemura
H
H
Tanaka
T
T
Nishikawa
S
S
Uesugi
S
S
Tanaka
A
A
Morikawa
M
M
Hayakawa
T
T
Ikehara
M
M
D000818:Animals; D001483:Base Sequence; D003553:Cystine / Q000235:genetics / Q000502:physiology*; D004220:Disulfides / Q000378:metabolism*; D013006:Growth Hormone / Q000138:chemical synthesis / Q000235:genetics / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation
D004220:Disulfides; D003553:Cystine; D013006:Growth Hormone