Baryshnikova Olga K, Sykes Brian D
Department of Biochemistry and Protein Engineering Network of Centres of Excellence, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
Protein Sci. 2006 Nov;15(11):2568-78. doi: 10.1110/ps.062255806.
SDF-1alpha is a member of the chemokine family implicated in various reactions in the immune system. The interaction of SDF-1alpha with its receptor, CXCR4, is responsible for metastasis of a variety of cancers. SDF-1alpha is also known to play a role in HIV-1 pathogenesis. The structures of SDF-1alpha determined by NMR spectroscopy have been shown to be monomeric while X-ray structures are dimeric. Biochemical data and in vivo studies suggest that dimerization is likely to be important for the function of chemokines. We report here the dynamics of SDF-1alpha determined through measurement of main chain (15)N NMR relaxation data. The data were obtained at several concentrations of SDF-1alpha and used to determine a dimerization constant of approximately 5 mM for a monomer-dimer equilibrium. The dimerization constant was subsequently used to extrapolate values for the relaxation data corresponding to monomeric SDF-1alpha. The experimental relaxation data and the extrapolated data for monomeric SDF-1alpha were analyzed using the model free approach. The model free analysis indicated that SDF-1alpha is rigid on the nano- to picosecond timescale with flexible termini. Several residues involved in the dimer interface display slow micro- to millisecond timescale motions attributable to chemical exchange such as monomer-dimer equilibrium. NMR relaxation measurements are shown to be applicable for studying oligomerization processes such as the dimerization of SDF-1alpha.
基质细胞衍生因子-1α（SDF-1α）是趋化因子家族的一员，参与免疫系统中的多种反应。SDF-1α与其受体CXCR4的相互作用导致多种癌症发生转移。已知SDF-1α在HIV-1发病机制中也发挥作用。通过核磁共振光谱法测定的SDF-1α结构显示为单体，而X射线结构则为二聚体。生化数据和体内研究表明，二聚化可能对趋化因子的功能很重要。我们在此报告通过测量主链（15）N核磁共振弛豫数据所确定的SDF-1α的动力学。这些数据是在几种SDF-1α浓度下获得的，并用于确定单体-二聚体平衡的二聚化常数约为5 mM。随后，利用该二聚化常数推断出对应单体SDF-1α弛豫数据的值。使用无模型方法分析了单体SDF-1α的实验弛豫数据和推断数据。无模型分析表明，SDF-1α在纳秒到皮秒时间尺度上是刚性的，但其末端是灵活的。二聚体界面中涉及的几个残基在微秒到毫秒时间尺度上显示出缓慢的运动，这归因于化学交换，如单体-二聚体平衡。核磁共振弛豫测量结果表明可用于研究诸如SDF-1α二聚化等寡聚化过程。
