Studies on the identity of the heme-binding cysteinyl residue in rabbit liver microsomal cytochrome P-450 isozyme 2.
Studies on the identity of the heme-binding cysteinyl residue in rabbit liver microsomal cytochrome P-450 isozyme 2.
复制标题
兔肝微粒体细胞色素 P-450 同工酶 2 中血红素结合半胱氨酰残基的研究。
DOI：
10.1016/0006-291x(85)91647-x
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发表时间：
1985
影响因子：
3.1
通讯作者：
Coon,MJ
中科院分区：
文献类型：
--
作者：
Black,SD;Coon,MJ
纯化的兔肝微粒体 P-450 同工酶 2 与 4,4'-二硫代双（2-硝基苯甲酸酯）（DTNB）的反应表现出一级动力学，并导致单个硫醇的修饰，但不会导致天然亚铁羰基谱的净损失。反应介质中同时包含磷脂和紧密结合的含氮配体 1-苯甲基咪唑，会产生 DTNB 修饰的爆发相，但化学计量仍然是每个多肽链修饰一个硫醇。同工酶 2 被 DTNB 和一溴二甲胺（一种硫醇基荧光试剂）快速标记的位点为 Cys152。获得的结果强烈表明 Cys152 不提供血红素铁原子的近端硫醇配体。由于 Cys152 代表 P-450 细胞色素中两个高度保守的含半胱氨酸区域之一，因此该兔细胞色素中的另一个区域可能包含 Cys436（对应于细菌 P-450 cam 中的 Cys355、大鼠 P-450 b 或 e 中的 Cys436、大鼠 P-450 c 中的 Cys461、大鼠中的 Cys456） P-450 d 或小鼠同工酶 3 和小鼠同工酶 1) 中的 Cys458 是血红素硫醇配体的来源。
The reaction of purified rabbit liver microsomal P-450 isozyme 2 with 4,4′-dithiobis(2-nitrobenzoate) (DTNB) exhibits first order kinetics and results in the modification of a single thiol, but causes no net loss of the native ferrous-carbonyl spectrum. Inclusion of both phospholipid and a tight-binding nitrogenous ligand, 1-benzylimidazole, in the reaction medium produces a burst-phase of DTNB modification, but the stoichiometry remains one thiol modified per polypeptide chain. The site of isozyme 2 rapidly labeled by DTNB and by monobromobimane, a fluorescent reagent for thiol groups, was shown to be Cys152. Results obtained strongly suggest that Cys152does not provide the proximal thiolate ligand to the heme iron atom. Since Cys152represents one of the two highly conserved cysteine-containing regions in the P-450 cytochromes, it appears likely that the other region, containing Cys436in this rabbit cytochrome (corresponding to Cys355in bacterial P-450 cam, Cys436in rat P-450 b or e, Cys461in rat P-450 c, Cys456in rat P-450 d or mouse isozyme 3, and Cys458in mouse isozyme 1) is the source of the thiolate ligand to the heme.