Baldwin G S, Grego B, Hearn M T, Knesel J A, Morgan F J, Simpson R J
Proc Natl Acad Sci U S A. 1983 Sep;80(17):5276-80. doi: 10.1073/pnas.80.17.5276.
In the present study, we have demonstrated that human growth hormone (hGH) can be phosphorylated by the epidermal growth factor (EGF)-stimulated tyrosine kinase of A431 cell membranes. Phosphotyrosine was the predominant phosphoamino acid released from phosphorylated hGH on partial acid hydrolysis. All five tyrosine-containing tryptic peptides of hGH are also phosphorylated by the EGF-stimulated tyrosine kinase. The highest phosphate incorporation was found for peptide T4 (residues 20-38), which is distinguished by a high frequency of acidic amino acids. The phosphorylated peptides have been characterized by HPLC and two-dimensional mapping on paper. Comparison with the labeled peptides obtained on tryptic digestion of phosphorylated hGH suggests that tyrosine phosphorylation is restricted to two tryptic peptides, T4 (tyrosine-28 or -35) and T6 (tyrosine-42). It is suggested that the absence of early insulin-like activity in the naturally occurring Mr 20,000 variant of hGH, which has an internal deletion spanning residues 32-46, may be a consequence of the loss of the tyrosine phosphorylation sites at residues 35 and 42.
在本研究中，我们已证明人生长激素（hGH）可被A431细胞膜上表皮生长因子（EGF）刺激的酪氨酸激酶磷酸化。磷酸酪氨酸是磷酸化hGH在部分酸水解时释放出的主要磷酸氨基酸。hGH的所有五个含酪氨酸的胰蛋白酶肽段也被EGF刺激的酪氨酸激酶磷酸化。肽段T4（第20 - 38位氨基酸残基）的磷酸掺入量最高，其特点是酸性氨基酸频率高。已通过高效液相色谱（HPLC）和纸上二维图谱对磷酸化肽段进行了表征。与磷酸化hGH胰蛋白酶消化后得到的标记肽段进行比较表明，酪氨酸磷酸化仅限于两个胰蛋白酶肽段，T4（酪氨酸 - 28或 - 35）和T6（酪氨酸 - 42）。有人提出，天然存在的Mr 20,000的hGH变体缺乏早期胰岛素样活性，该变体有一个跨越第32 - 46位氨基酸残基的内部缺失，这可能是由于第35和42位氨基酸残基处酪氨酸磷酸化位点缺失的结果。
