Baker Joseph L, Courtemanche Naomi, Parton Daniel L, McCullagh Martin, Pollard Thomas D, Voth Gregory A
Department of Chemistry, The University of Chicago, 5735 S. Ellis Avenue, Chicago, IL 60637, USA; Institute for Biophysical Dynamics, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA; James Franck Institute, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA; Computation Institute, The University of Chicago, 5735 S. Ellis Avenue, Chicago, IL 60637, USA.
Department of Molecular, Cellular and Developmental Biology, Yale University, P.O. Box 208103, New Haven, CT 06520-8103, USA.
Structure. 2015 Jan 6;23(1):68-79. doi: 10.1016/j.str.2014.10.014. Epub 2014 Dec 4.
Formins catalyze nucleation and growth of actin filaments. Here, we study the structure and interactions of actin with the FH2 domain of budding yeast formin Bni1p. We built an all-atom model of the formin dimer on an Oda actin filament 7-mer and studied structural relaxation and interprotein interactions by molecular dynamics simulations. These simulations produced a refined model for the FH2 dimer associated with the barbed end of the filament and showed electrostatic interactions between the formin knob and actin target-binding cleft. Mutations of two formin residues contributing to these interactions (R1423N, K1467L, or both) reduced the interaction energies between the proteins, and in coarse-grained simulations, the formin lost more interprotein contacts with an actin dimer than with an actin 7-mer. Biochemical experiments confirmed a strong influence of these mutations on Bni1p-mediated actin filament nucleation, but not elongation, suggesting that different interactions contribute to these two functions of formins.
成肌蛋白催化肌动蛋白丝的成核和生长。在此,我们研究了肌动蛋白与芽殖酵母成肌蛋白Bni1p的FH2结构域的结构及相互作用。我们在一个小田肌动蛋白丝七聚体上构建了成肌蛋白二聚体的全原子模型,并通过分子动力学模拟研究了结构弛豫和蛋白间相互作用。这些模拟产生了一个与肌动蛋白丝的尖端相关的FH2二聚体的优化模型,并显示了成肌蛋白旋钮与肌动蛋白靶标结合裂隙之间的静电相互作用。对促成这些相互作用的两个成肌蛋白残基进行突变(R1423N、K1467L或两者皆有)会降低蛋白质之间的相互作用能,并且在粗粒度模拟中,与肌动蛋白二聚体相比,成肌蛋白与肌动蛋白七聚体失去的蛋白间接触更多。生化实验证实了这些突变对Bni1p介导的肌动蛋白丝成核有强烈影响,但对伸长没有影响,这表明不同的相互作用对成肌蛋白的这两种功能有贡献。