Layton J E, Iaria J, Smith D K, Treutlein H R
Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, P. O. Box 2008, Royal Melbourne Hospital, Parkville, Australia 3050.
J Biol Chem. 1997 Nov 21;272(47):29735-41. doi: 10.1074/jbc.272.47.29735.
Granulocyte colony-stimulating factor (G-CSF) initiates its effects on cells of the neutrophil lineage by inducing formation of a homodimeric receptor complex. The structure of the G-CSF receptor has not yet been determined, therefore we used molecular modeling to identify regions of the receptor that were likely to be involved in ligand binding. The G-CSF receptor sequence was aligned with all the available sequences of the gp130 and growth hormone receptor families and a model of the cytokine receptor homologous domain was constructed, based on the growth hormone receptor structure. Alanine substitution mutagenesis was performed on loops and individual residues that were predicted to bind ligand. Mutant receptors were expressed in factor-dependent Ba/F3 cells and assessed for proliferation response and ligand binding. Six residues were identified that significantly reduced receptor function, with Arg288 in the F'-G' loop having the greatest effect. These residues formed a binding face on the receptor model resembling the growth hormone receptor site, which suggests that the model is reasonable. However, electrostatic analysis of the model provided further evidence that the mechanism of receptor dimerization is different from that of the growth hormone receptor.
粒细胞集落刺激因子（G-CSF）通过诱导同源二聚体受体复合物的形成，对中性粒细胞系细胞发挥作用。G-CSF受体的结构尚未确定，因此我们利用分子建模来识别受体中可能参与配体结合的区域。将G-CSF受体序列与gp130和生长激素受体家族的所有可用序列进行比对，并基于生长激素受体结构构建了细胞因子受体同源结构域模型。对预测与配体结合的环和单个残基进行丙氨酸替代诱变。突变受体在因子依赖性Ba/F3细胞中表达，并评估其增殖反应和配体结合情况。鉴定出六个显著降低受体功能的残基，其中F'-G'环中的Arg288影响最大。这些残基在受体模型上形成了一个类似于生长激素受体位点的结合面，这表明该模型是合理的。然而，对该模型的静电分析提供了进一步的证据，表明受体二聚化机制与生长激素受体不同。
