MacKintosh R W, Dalby K N, Campbell D G, Cohen P T, Cohen P, MacKintosh C
Department of Biochemistry, University of Dundee, Scotland, UK.
FEBS Lett. 1995 Sep 11;371(3):236-40. doi: 10.1016/0014-5793(95)00888-g.
The interaction between protein phosphatase 1 (PP1) and microcystin (MC) was stable in 1% SDS or 70% formic acid indicative of a covalent interaction. Here we isolate the MC-binding peptide and demonstrate that Cys273 of PP1 binds covalently to the methyl-dehydroalanine (Mdha) residue of the toxin. Mutation of Cys273 to Ala, Ser or Leu abolished covalent binding to MC, as did reduction of the Mdha residue of the toxin with ethanethiol. The abolition of covalent binding increased the IC50 for toxin inhibition of PP1 by 5- to 20-fold. The covalent binding of MC to protein serine/threonine phosphatases explains the failure to detect this toxin post-mortem in suspected cases of MC poisoning.
蛋白磷酸酶1（PP1）与微囊藻毒素（MC）之间的相互作用在1%十二烷基硫酸钠（SDS）或70%甲酸中稳定，表明存在共价相互作用。在此，我们分离出了MC结合肽，并证明PP1的半胱氨酸273（Cys273）与毒素的甲基脱氢丙氨酸（Mdha）残基共价结合。将Cys273突变为丙氨酸（Ala）、丝氨酸（Ser）或亮氨酸（Leu）会消除与MC的共价结合，用乙硫醇还原毒素的Mdha残基也会如此。共价结合的消除使毒素抑制PP-1的半数抑制浓度（IC50）增加了5至20倍。MC与蛋白质丝氨酸/苏氨酸磷酸酶的共价结合解释了在疑似MC中毒病例的尸检中未能检测到这种毒素的原因。
