Berlett B S, Friguet B, Yim M B, Chock P B, Stadtman E R
Laboratory of Biochemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892-0342, USA.
Proc Natl Acad Sci U S A. 1996 Mar 5;93(5):1776-80. doi: 10.1073/pnas.93.5.1776.
Treatment of Escherichia coli glutamine synthetase (GS) with peroxynitrite leads to nitration of some tyrosine residues and conversion of some methionine residues to methionine sulfoxide (MSOX) residues. Nitration, but not MSOX formation, is stimulated by Fe-EDTA. In the absence of Fe-EDTA, nitration of only one tyrosine residue per subunit of unadenylylated GS leads to changes in divalent cation requirement, pH-activity profile, affinity for ADP, and susceptibility to feedback inhibition by end products (tryptophan, AMP, CTP), whereas nitration of one tyrosine residue per subunit in the adenylylated GS leads to complete loss of catalytic activity. In the presence of Fe-EDTA, nitration is a more random process: nitration of five to six tyrosine residues per subunit is needed to convert unadenylylated GS to the adenylylated configuration. These results and the fact that nitration of tyrosine residues is an irreversible process serve notice that the regulatory function of proteins that undergo phosphorylation or adenylylation in signal transduction cascades might be seriously compromised by peroxynitrite-promoted nitration.
用过氧亚硝酸根处理大肠杆菌谷氨酰胺合成酶（GS）会导致一些酪氨酸残基发生硝化作用，并使一些甲硫氨酸残基转化为甲硫氨酸亚砜（MSOX）残基。铁螯合剂乙二胺四乙酸（Fe-EDTA）会刺激硝化作用，但不会刺激MSOX的形成。在没有Fe-EDTA的情况下，未腺苷酸化的GS每个亚基仅一个酪氨酸残基发生硝化作用就会导致二价阳离子需求、pH-活性曲线、对ADP的亲和力以及对终产物（色氨酸、AMP、CTP）反馈抑制的敏感性发生变化，而腺苷酸化的GS每个亚基一个酪氨酸残基发生硝化作用则会导致催化活性完全丧失。在有Fe-EDTA存在的情况下，硝化作用是一个更随机的过程：未腺苷酸化的GS要转化为腺苷酸化构型，每个亚基需要五到六个酪氨酸残基发生硝化作用。这些结果以及酪氨酸残基硝化作用是一个不可逆过程这一事实表明，在信号转导级联反应中经历磷酸化或腺苷酸化的蛋白质的调节功能可能会因过氧亚硝酸根促进的硝化作用而受到严重损害。
