Kukol A, Adams P D, Rice L M, Brunger A T, Arkin T I
Cambridge Centre for Molecular Recognition and Department of Biochemistry University of Cambridge, 80 Tennis Court Road, Cambridge, CB2 1GA, UK.
J Mol Biol. 1999 Feb 26;286(3):951-62. doi: 10.1006/jmbi.1998.2512.
The 97-residue M2 protein from Influenza A virus forms H+-selective ion channels which can be attributed solely to the homo-tetrameric alpha-helical transmembrane domain. Site-directed infrared dichroism spectra were obtained for the transmembrane domain of M2, reconstituted in lipid vesicles. Data analysis yielded the helix tilt angle beta=31.6(+/-6.2) degrees and the rotational pitch angle about the helix axis for residue Ala29 omegaAla29=-59.8(+/-9.9) degrees, whereby omega is defined as zero for a residue located in the direction of the helix tilt. A structure was obtained from an exhaustive molecular dynamics global search protocol in which the orientational data are utilised directly as an unbiased refinement energy term. Orientational refinement not only allowed selection of a unique structure but could also be shown to increase the convergence towards that structure during the molecular dynamics procedure. Encouragingly, the structure obtained is highly consistent with all available mutagenesis and conductivity data and offers a direct chemical insight that relates the altered functionality of the channel to its structure.
甲型流感病毒的97个氨基酸残基的M2蛋白形成了H⁺选择性离子通道，这完全归因于同四聚体α-螺旋跨膜结构域。通过脂质体中重构的M2跨膜结构域获得了定点红外二向色光谱。数据分析得出螺旋倾斜角β = 31.6（±6.2）度，以及残基Ala29处围绕螺旋轴的旋转螺距角ωAla29 = -59.8（±9.9）度，其中对于位于螺旋倾斜方向的残基，ω定义为零。通过详尽的分子动力学全局搜索协议获得了一种结构，其中取向数据直接用作无偏细化能量项。取向细化不仅允许选择独特的结构，而且还可以证明在分子动力学过程中增加了向该结构的收敛性。令人鼓舞的是，获得的结构与所有可用的诱变和电导率数据高度一致，并提供了直接的化学见解，将通道功能的改变与其结构联系起来。
