Targeting of NH2-terminal-processed microsomal protein to mitochondria: a novel pathway for the biogenesis of hepatic mitochondrial P450MT2.
Targeting of NH2-terminal-processed microsomal protein to mitochondria: a novel pathway for the biogenesis of hepatic mitochondrial P450MT2.
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DOI：
10.1083/jcb.139.3.589
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发表时间：
1997-11-03
影响因子：
7.8
通讯作者：
Avadhani, NG
中科院分区：
文献类型：
--
作者：
Addya, S;Anandatheerthavarada, HK;Biswas, G;Bhagwat, SV;Mullick, J;Avadhani, NG
细胞色素 P4501A1 是一种肝脏微粒体膜结合酶，可被各种外源物质高度诱导。该 P450 的两种 NH2 末端截短形式，称为 P450MT2a 和 MT2b，也被发现位于 β-萘黄酮诱导肝脏的线粒体中。在本文中，我们证明 P4501A1 具有嵌合 NH2 末端信号，有助于蛋白质靶向 ER 和线粒体。 P4501A1 的 NH2 末端 30 个氨基酸片段被认为为 ER 膜插入提供信号并停止转移。本研究提供的证据表明，跨膜结构域 COOH 末端的序列基序（残基 33-44）在体内和体外条件下均可作为线粒体靶向信号，并且位置 34 和 39 处的带正电残基对于线粒体靶向至关重要。结果表明，25% 的 P4501A1 新生链逃脱了内质网膜插入，并由肝胞质内切蛋白酶进行加工。我们假设 NH2 末端蛋白水解裂解激活了一个神秘的线粒体靶向信号。免疫荧光显微镜显示，瞬时表达的 P4501A1 的一部分与线粒体特异性标记蛋白细胞色素氧化酶亚基 I 共定位。线粒体相关的 MT2a 和 MT2b 位于内膜区室中，通过完整线粒体和线粒体中有限蛋白水解的抗性进行测试。 线粒体。因此，我们的结果描述了一种新的机制，通过该机制，具有嵌合信号序列的蛋白质靶向内质网以及线粒体。
Cytochrome P4501A1 is a hepatic, microsomal membrane–bound enzyme that is highly induced by various xenobiotic agents. Two NH2-terminal truncated forms of this P450, termed P450MT2a and MT2b, are also found localized in mitochondria from β-naphthoflavone–induced livers. In this paper, we demonstrate that P4501A1 has a chimeric NH2-terminal signal that facilitates the targeting of the protein to both the ER and mitochondria. The NH2-terminal 30–amino acid stretch of P4501A1 is thought to provide signals for ER membrane insertion and also stop transfer. The present study provides evidence that a sequence motif immediately COOH-terminal (residues 33–44) to the transmembrane domain functions as a mitochondrial targeting signal under both in vivo and in vitro conditions, and that the positively charged residues at positions 34 and 39 are critical for mitochondrial targeting. Results suggest that 25% of P4501A1 nascent chains, which escape ER membrane insertion, are processed by a liver cytosolic endoprotease. We postulate that the NH2-terminal proteolytic cleavage activates a cryptic mitochondrial targeting signal. Immunofluorescence microscopy showed that a portion of transiently expressed P4501A1 is colocalized with the mitochondrial-specific marker protein cytochrome oxidase subunit I. The mitochondrial-associated MT2a and MT2b are localized within the inner membrane compartment, as tested by resistance to limited proteolysis in both intact mitochondria and mitoplasts. Our results therefore describe a novel mechanism whereby proteins with chimeric signal sequence are targeted to the ER as well as to the mitochondria.
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影响因子：
7.8
作者：
GILMORE, R;WALTER, P;BLOBEL, G
通讯作者：
BLOBEL, G
DOI：
10.1073/pnas.91.25.11973
发表时间：
1994-12-06
影响因子：
11.1
作者：
LITHGOW, T;JUNNE, T;SCHATZ, G
通讯作者：
SCHATZ, G
影响因子：
11.4
作者：
Belin, D;Bost, S;Strub, K
通讯作者：
Strub, K
影响因子：
3.9
作者：
BHAGWAT, SV;BOYD, MR;RAVINDRANATH, V
通讯作者：
RAVINDRANATH, V
影响因子：
3.9
作者：
HONKAKOSKI, P;KOJO, A;LANG, MA
通讯作者：
LANG, MA