Catling A D, Reuter C W, Cox M E, Parsons S J, Weber M J
Department of Microbiology, University of Virginia Health Sciences Center, Charlottesville 22908.
J Biol Chem. 1994 Nov 25;269(47):30014-21.
A classical biochemical approach was taken to identify mitogen-activated protein kinase kinase (MEK) activators in bovine brain. Fractionation revealed the presence of one major MEK-stimulating activity that was distinct from c-Raf-1 and MEK kinase. Similar results were obtained using bovine adrenal chromaffin cells, and in both cases, immunoblotting and immunoprecipitation experiments demonstrated co-purification of MEK activator with B-Raf. Partially purified MEK activator stimulated phosphorylation of MEK1 on residues tentatively identified as serine 218 and serine 222. Little or no MEK activator was associated with c-Raf-1 in bovine brain or chromaffin cells, although this protein was expressed, suggesting that B-Raf might be the major MEK activator in cells of neural origin.
采用经典的生化方法在牛脑中鉴定丝裂原活化蛋白激酶激酶（MEK）激活剂。分级分离显示存在一种主要的MEK刺激活性，它不同于c-Raf-1和MEK激酶。使用牛肾上腺嗜铬细胞也获得了类似的结果，并且在这两种情况下，免疫印迹和免疫沉淀实验都证明MEK激活剂与B-Raf共纯化。部分纯化的MEK激活剂刺激了MEK1在暂定为丝氨酸218和丝氨酸222的残基上的磷酸化。尽管牛脑或嗜铬细胞中表达了c-Raf-1，但很少或没有MEK激活剂与之相关，这表明B-Raf可能是神经源性细胞中的主要MEK激活剂。
