Tantos Agnes, Szrnka Kriszta, Szabo Beata, Bokor Monika, Kamasa Pawel, Matus Peter, Bekesi Angela, Tompa Kalman, Han Kyou-Hoon, Tompa Peter
Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Budapest, Hungary.
Biochim Biophys Acta. 2013 Jan;1834(1):342-50. doi: 10.1016/j.bbapap.2012.08.005. Epub 2012 Aug 11.
Human nucleolar phosphoprotein p140 (hNopp 140) is a highly phosphorylated protein inhibitor of casein kinase 2 (CK2). As in the case of many kinase-inhibitor systems, the inhibitor has been described to belong to the family of intrinsically disordered proteins (IDPs), which often utilize transient structural elements to bind their cognate enzyme. Here we investigated the structural status of this protein both to provide distinct lines of evidence for its disorder and to point out its transient structure potentially involved in interactions and also its tendency to aggregate. Structural disorder of hNopp140 is apparent by its anomalous electrophoretic mobility, protease sensitivity, heat stability, hydrodynamic behavior on size-exclusion chromatography, (1)H NMR spectrum and differential scanning calorimetry scan. hNopp140 has a significant tendency to aggregate and the change of its circular dichroism spectrum in the presence of 0-80% TFE suggests a tendency to form local helical structures. Wide-line NMR measurements suggest the overall disordered character of the protein. In all, our data suggest that this protein falls into the pre-molten globule state of IDPs, with a significant tendency to become ordered in the presence of its partner as demonstrated in the presence of transcription factor IIB (TFIIB).
人类核仁磷蛋白p140（hNopp 140）是酪蛋白激酶2（CK2）的一种高度磷酸化的蛋白抑制剂。与许多激酶-抑制剂系统一样，该抑制剂被描述为属于内在无序蛋白（IDP）家族，这类蛋白通常利用瞬时结构元件来结合其同源酶。在此，我们研究了这种蛋白的结构状态，既为其无序性提供不同的证据线索，又指出其可能参与相互作用的瞬时结构以及其聚集倾向。hNopp140的结构无序通过其异常的电泳迁移率、蛋白酶敏感性、热稳定性、尺寸排阻色谱上的流体动力学行为、（1）H NMR谱和差示扫描量热扫描得以体现。hNopp140具有显著的聚集倾向，在存在0 - 80%三氟乙醇（TFE）的情况下其圆二色光谱的变化表明它有形成局部螺旋结构的倾向。宽线NMR测量表明该蛋白整体具有无序特征。总之，我们的数据表明这种蛋白属于IDP的前熔球态，在其伴侣存在时（如在转录因子IIB（TFIIB）存在时所证明的）有显著的有序化倾向。
