Bundgaard J R, Vuust J, Rehfeld J F
Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, DK-2100 Copenhagen, Denmark.
J Biol Chem. 1997 Aug 29;272(35):21700-5. doi: 10.1074/jbc.272.35.21700.
Tyrosine sulfation is an ubiquitous modification of proteins synthesized along the secretory pathway. It enhances protein-protein interactions and may be necessary for the bioactivity of secreted proteins and peptides. To predict tyrosine sulfation, a consensus has been proposed based on sequence comparisons of known substrates and on in vitro studies using synthetic peptides. This consensus predicts the presence of acidic residues on the amino-terminal side of the target tyrosine as the key feature. Using site-directed mutagenesis, we have examined the role of residues neighboring the sulfation site of an intact protein, human progastrin, in vivo. The results show that the charge of the residue in the amino-terminal position (-1) of the tyrosine is critical and can be neutral or acidic, whereas a basic residue abolishes sulfation. In addition, the degree of sulfation is influenced by the residues in positions -2 and -3. Hence, surprisingly a basic residue in position -2 enhances sulfation. Our data suggest a considerably broader range of substrates for the tyrosylprotein sulfotransferase than hitherto assumed and that the tyrosylprotein sulfotransferase is cell-specifically expressed.
酪氨酸硫酸化是沿分泌途径合成的蛋白质普遍存在的一种修饰。它增强了蛋白质-蛋白质相互作用，可能是分泌蛋白和肽生物活性所必需的。为了预测酪氨酸硫酸化，基于已知底物的序列比较和使用合成肽的体外研究，人们提出了一种一致性规则。该规则预测目标酪氨酸氨基末端侧存在酸性残基是关键特征。我们利用定点诱变技术，在体内研究了完整蛋白人胃泌素硫酸化位点附近残基的作用。结果表明，酪氨酸氨基末端位置（-1）残基的电荷至关重要，可为中性或酸性，而碱性残基则会消除硫酸化。此外，硫酸化程度受-2和-3位置残基的影响。因此，令人惊讶的是，-2位置的碱性残基会增强硫酸化。我们的数据表明，酪氨酰蛋白硫酸转移酶的底物范围比迄今所认为的要广泛得多，并且酪氨酰蛋白硫酸转移酶是细胞特异性表达的。
