Glocker M O, Arbogast B, Schreurs J, Deinzer M L
Department of Agricultural Chemistry, Oregon State University, Corvallis 97331.
Biochemistry. 1993 Jan 19;32(2):482-8. doi: 10.1021/bi00053a012.
The disulfide bridges in recombinant human macrophage colony stimulating factor (rhM-CSF), a 49-kDa homodimeric protein, were assigned. The 18 cysteines in the dimer form three intermolecular and two sets of three intramolecular disulfide bonds. The intermolecular disulfide bridges hold the dimer together and form symmetric bonds in which Cys31 and Cys157/Cys159 from one monomer unit are linked to the corresponding cysteines of the second monomer. The intramolecular disulfide bonds are located between Cys7-Cys90, Cys48-Cys139, and Cys102-Cys146, respectively. The resistance of native M-CSF to proteolytic cleavage was overcome by an initial chemical cleavage reaction using BrCN. The close proximity of four cysteines (Cys139, Cys146, Cys157, and Cys159) results in a tight core complex that makes the protein undigestable for most proteases. Digestion using endoprotease Asp-N resulted in cleavage at Asp156 near the C-terminal end of this region, thereby opening the complex structure.
重组人巨噬细胞集落刺激因子（rhM-CSF）是一种49 kDa的同二聚体蛋白，其二硫键已被确定。二聚体中的18个半胱氨酸形成了三个分子间二硫键和两组三个分子内二硫键。分子间二硫键将二聚体维系在一起并形成对称键，其中一个单体单元的Cys31和Cys157/Cys159与第二个单体的相应半胱氨酸相连。分子内二硫键分别位于Cys7-Cys90、Cys48-Cys139和Cys102-Cys146之间。通过使用溴化氰的初始化学裂解反应克服了天然M-CSF对蛋白水解裂解的抗性。四个半胱氨酸（Cys139、Cys146、Cys157和Cys159）紧密相邻形成了一个紧密的核心复合物，使得该蛋白对大多数蛋白酶来说难以消化。使用内切蛋白酶Asp-N进行消化导致在该区域C末端附近的Asp156处裂解，从而打开复合物结构。
