兔肝微粒体中苯巴比妥诱导的细胞色素P-450（同工酶2）的完整氨基酸序列及预测的膜拓扑结构
Complete amino acid sequence and predicted membrane topology of phenobarbital-induced cytochrome P-450 (isozyme 2) from rabbit liver microsomes.
作者信息
Tarr G E, Black S D, Fujita V S, Coon M J
出版信息
Proc Natl Acad Sci U S A. 1983 Nov;80(21):6552-6. doi: 10.1073/pnas.80.21.6552.
The complete amino acid sequence of phenobarbital-induced isozyme 2 of rabbit liver microsomal cytochrome P-450 (P-450LM2) is presented. The polypeptide consists of 491 residues with a calculated Mr of 55,755. The rabbit isozyme is 77% identical to the corresponding rat cytochrome, P-450b, as deduced from cDNA, with 96% of the hydrophobic, 88% of the anionic, and 83% of the cationic positions conserved. The secondary structure of isozyme 2 was predicted and a model was developed for the membrane topology of this cytochrome. Of the two highly conserved cysteinyl peptides in P-450LM2, P-450b, and bacterial P-450cam, we favor, on the basis of our model, the one nearer the NH2 terminus (Cys-152 in P-450LM2) as the source of the thiolate ligand to the heme iron atom. The recently reported sequence of the apparently identical protein [Heinemann, F. S. & Ozols, J. (1983) J. Biol. Chem. 258, 4195-4201] has two fewer residues and differs in 14 other amino acid assignments.
本文给出了苯巴比妥诱导的兔肝微粒体细胞色素P-450（P-450LM2）同工酶2的完整氨基酸序列。该多肽由491个残基组成，计算所得的分子量为55,755。根据cDNA推导，兔同工酶与相应的大鼠细胞色素P-450b有77%的同源性，其中96%的疏水位置、88%的阴离子位置和83%的阳离子位置保守。预测了同工酶2的二级结构，并构建了该细胞色素膜拓扑结构的模型。在P-450LM2、P-450b和细菌P-450cam中高度保守的两个半胱氨酸肽段中，基于我们的模型，我们倾向于认为靠近NH2末端的那个（P-450LM2中的Cys-152）是与血红素铁原子形成硫醇盐配体的来源。最近报道的序列与该明显相同的蛋白质[Heinemann, F. S. & Ozols, J. (1983) J. Biol. Chem. 258, 4195 - 4201]相比，残基少了两个，且在其他14个氨基酸位点上存在差异。
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