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首页> 外文期刊>Biophysical Chemistry: An International Journal Devoted to the Physical Chemistry of Biological Phenomena >A universal system for the transport of redox proteins: early roots and latest developments.
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A universal system for the transport of redox proteins: early roots and latest developments.

机译：氧化还原蛋白运输的通用系统：早期根源和最新发展。

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摘要

The transport of proteins binding redox cofactors across a biological membrane is complicated by the fact that insertion of the redox cofactor is often a cytoplasmic process. These cytoplasmically assembled redox proteins must thus be transported in partially or completely folded form. The need for a special transport system for redox proteins was first recognized for periplasmic hydrogenases in gram-negative bacteria. These enzymes, which catalyze the reaction H2 <--> 2H+ + 2e, are composed of a large and a small subunit. Only the small subunit has an unusually long signal sequence of 30-50 amino acid residues, characterized by a conserved motif (S/T)-R-R-x-F-L-K at the N-terminus. This sequence directs export of the large and small subunit complex to the periplasm. Sequencing of microbial genes and genomes has shown that signal sequences with this conserved motif, now referred to as twin-arginine leaders, occur ubiquitously and export different classes of redox proteins, containing iron sulfur clusters, molybdopterin cofactors, polynuclear copper sites or flavin adenine dinucleotide. Mutations in an Escherichia coli operon referred to as mtt (membrane targeting and translocation) or tat (twin arginine translocation) are pleiotropic, i.e. these prevent the expression of a variety of periplasmic oxido-reductases in functional form. The Mtt or Tat pathway is distinct from the well-known Sec pathway and occurs ubiquitously in prokaryotes. The fact that its component proteins share sequence homology with proteins of the delta pH pathway for protein transport associated with chloroplast thylakoid assembly, illustrates the universal nature of this novel protein translocation system.
机译：结合氧化还原辅因子的插入通常是细胞质过程这一事实使结合氧化还原辅因子的蛋白质的运输跨生物膜变得复杂。这些细胞质组装的氧化还原蛋白因此必须以部分或完全折叠的形式运输。对于革兰氏阴性细菌的周质氢化酶，首先认识到需要特殊的氧化还原蛋白转运系统。这些催化H2→2H ++ 2e反应的酶由一个大亚基和一个小亚基组成。只有小亚基具有30-50个氨基酸残基的异常长的信号序列，其特征是N端的保守基序（S / T）-R-R-x-F-L-K。该序列指导大亚基复合物和小亚基复合物向周质的输出。微生物基因和基因组的测序表明，具有这种保守基序的信号序列（现在称为双精氨酸前导序列）无处不在，并输出不同类别的氧化还原蛋白，其中包含铁硫簇，钼蝶呤辅因子，多核铜位点或黄素腺嘌呤二核苷酸。在大肠杆菌操纵子中称为mtt（膜靶向和转运）或tat（双精氨酸转运）的突变是多效性的，即，这些突变阻止了功能形式的多种周质氧化还原酶的表达。 Mtt或Tat途径不同于众所周知的Sec途径，并普遍存在于原核生物中。其组成蛋白与δpH途径的蛋白具有与叶绿体类囊体组装相关的蛋白运输共享序列同源性这一事实，说明了这种新型蛋白易位系统的普遍性。

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