Factor B and energy coupling in mitochondria

线粒体中的因子 B 和能量耦合

基本信息

批准号：
7253358
负责人：
GRIGORY I BELOGRUDOV
金额：
$ 19.78万
依托单位：
UNIVERSITY OF CALIFORNIA LOS ANGELES
依托单位国家：
美国
项目类别：
财政年份：
2003
资助国家：
美国
起止时间：
2003-07-01 至 2009-06-30
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): In mitochondria, substrate oxidation by multisubunit complexes of the electron transport chain is coupled to ATP synthesis by the ATP synthase complex via an electrochemical proton gradient, Delta-mu-H+, across the mitochondrial inner membrane. The ability to synthesize ATP, establish Delta-mu-H+ and catalyze the energy-linked reactions is lost in bovine heart submitochondrial particles sonicated at pH 8.8 in the presence of 0.6 mM EDTA, due to proton leakiness of the mitochondrial inner membrane. Recently, we cloned and expressed in bacteria a human mitochondrial polypeptide, factor B, that efficiently restored all the energy-linked reactions, including the ATP synthesis, in the pH 8.8/EDTA treated submitochondrial particles. Because factor B coupling activity is similar to that of low amounts of oligomycin, a specific inhibitor of proton translocation through the membrane sector F-0 of ATP synthase, we propose that factor B is a regulatory component of mitochondrial ATP synthase, loosely associated with F-0 sector. We hypothesize that in mitochondria, factor B is involved in regulation of proton flux through F-0 sector coupled to ATP synthesis in the active site of the enzyme. We further hypothesize that via redox status of its essential thiols, specifically a vicinal dithiol, factor B acts as a "pressure valve" for maintaining proton-motive force below the threshold that favors production of reactive oxygen species in mitochondria, by inducing a mild uncoupling of the organelle. The following specific aims are proposed: 1) To characterize the interaction of factor B with the membrane sector F-0 in the membrane bound and detergent solubilized ATP synthase complex; and 2) To elucidate the structure-function relationship of the vicinal dithiol motif found in the amino acid sequence of the mature factor B, and the role it plays in the factor B sensitivity toward Cd 2+ and phenylarsine oxide, both of which uncouple oxidative phosphorylation in mitochondria. The proposed research is expected to advance the knowledge of the molecular mechanisms of energy transfer and conservation in mitochondria, and shed light on the role of mitochondria in a number of human disorders.

描述（由申请人提供）：在线粒体中，通过电化学质子梯度，Delta-Mu-H+，通过ATP合酶络合物偶联，电子传输链的多基型复合物与ATP合成偶联。合成ATP，建立delta-mu-h+并催化能量连接反应的能力在牛心脏sisbtsochondrial颗粒中由于pH 8.8而在0.6 mM EDTA的情况下，由于线粒体内膜的质子泄漏，因此在pH 8.8处超声处理。最近，我们在细菌中克隆并表达了人的线粒体多肽因子B，在pH 8.8/EDTA处理过的sistmochochondrial颗粒中，有效地恢复了包括ATP合成在内的所有能量连接的反应。由于因子B偶联活性与低寡霉素的少量抑制剂相似，这是ATP合酶的质子易位的特异性抑制剂，因此我们提出因子B是线粒体ATP ATP合酶的调节成分，与F-0扇区松散相关。我们假设在线粒体中，因子B参与了通过酶的活性位点与ATP合成的F-0扇形对质子通量的调节。我们进一步假设，通过其必需硫醇的氧化还原状态，特别是替代二硫醇，因子B充当一种“压力阀”，可通过诱导细胞器的轻度解开线粒体中的质子 - 动力来维持质子 - 动力。提出了以下具体目的：1）表征因因子B与膜扇形F-0的相互作用在膜结合和洗涤剂溶解的ATP合酶复合物中的相互作用； 2）为了阐明在成熟因子B的氨基酸序列中发现的替代二硫醇基序的结构 - 功能关系，及其在对CD 2+和苯基烷氧化物因子B敏感性中所扮演的作用，这两者都在线粒体中取消了无偶发的氧化磷酸化。拟议的研究有望提高线粒体能量转移和保护的分子机制的了解，并阐明线粒体在许多人类疾病中的作用。