The Functions and Properties of Nonmuscle Myosin Heavy Chains

我们使用杆状病毒/Sf9系统成功地表达和纯化了三个全长人非肌球蛋白II （NM II）蛋白及其轻链。对这三种类似物的酶学性质和结构性质进行了表征。虽然每个纳米II都能形成双极细丝，但由IIC形成的细丝往往比IIA和IIB形成的细丝含有更少的组成分子。在ATP存在的情况下，所有的类似物都采用紧凑的构象。调节轻链的磷酸化导致组装成细丝，在ATP存在的情况下与肌动蛋白结合。与肌动蛋白丝相互作用的性质显示了不同的类比，在等效条件下表现出不同的肌动蛋白结合行为。数据表明，虽然纳米IIA和IIB形成的细丝具有相似的性能，但纳米IIC形成的细丝不太适合细胞内的张力维持等作用。我们现在正在扩展这些研究，包括使用已被证明在人类综合征中起致病作用的突变型纳米ii。

We have successfully expressed and purified the three full-length human nonmuscle myosin II (NM II) proteins with their light chains, using the baculovirus/Sf9 system. The enzymatic and structural properties of the three paralogs were characterized. Although each NM II is capable of forming bipolar filaments, those formed by IIC tend to contain fewer constituent molecules than those of IIA and IIB. All paralogs adopt the compact conformation in the presence of ATP. Phosphorylation of the regulatory light chain leads to assembly into filaments, which bind to actin in the presence of ATP. The nature of interactions with actin filaments is shown with different paralogs exhibiting different actin binding behaviors under equivalent conditions. The data show that although NM IIA and IIB form filaments with similar properties, NM IIC forms filaments that are less well suited to roles such as tension maintenance within the cell. We are now extending these studies to include the use of mutant NM IIs that have been shown to play a causative role in human syndromes.