Molecular cloning, sequencing, and expression of omp-40, the gene coding for the major outer membrane protein from the acidophilic bacterium Thiobacillus ferrooxidans
Molecular cloning, sequencing, and expression of omp-40, the gene coding for the major outer membrane protein from the acidophilic bacterium Thiobacillus ferrooxidans
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DOI：
10.1128/aem.66.6.2318-2324.2000
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发表时间：
2000-06-01
影响因子：
4.4
通讯作者：
Jerez, CA
中科院分区：
文献类型：
--
作者：
Guiliani, N;Jerez, CA
氧化亚铁硫杆菌是工业生物采矿中重要的化能自养菌之一。这种微生物的一些表面成分可能参与适应其酸性环境和细菌-矿物相互作用。我们分离并鉴定了氧化亚铁硫杆菌主要外膜蛋白Omp 40基因，推导的Omp 40蛋白的氨基酸序列为382个氨基酸，计算的分子量为40，095.7。Omp 40形成约120 kDa的低聚结构，其通过在十二烷基硫酸钠存在下加热解离成单体（40 kDa）。Omp 40氨基酸序列与肠杆菌孔蛋白的同源性仅为22%。然而，该序列与几种OmpC孔蛋白的序列的多重比对显示了氧化亚铁硫杆菌表面蛋白的几个重要保守特征，如16条跨膜β链，8个环，包括一个大的外部L3环，和八个转角，这使我们能够提出一个假定的16链β-桶孔蛋白结构的蛋白质。这些结果与以前已知的Omp 40在平面脂质双层中形成离子通道的能力一起强烈支持其在这种化能自养嗜酸微生物中作为孔蛋白的作用。Omp 40蛋白的一些特征，如存在推定的L3环，估计等电点为7.21，使我们能够推测这可能是嗜酸性T.铁氧化物，以防止质子穿过其外膜的自由运动。
Thiobacillus ferrooxidans is one of the chemolithoautotrophic bacteria important in industrial biomining operations. Some of the surface components of this microorganism are probably involved in adaptation to their acidic environment and in bacterium-mineral interactions. We have isolated and characterized omp40, the gene coding for the major outer membrane protein from T, ferrooxidans, The deduced amino acid sequence of the Omp40 protein has 382 amino acids and a calculated molecular weight of 40,095.7. Omp40 forms an oligomeric structure of about 120 kDa that dissociates into the monomer (40 kDa) by heating in the presence of sodium dodecyl sulfate. The degree of identity of Omp40 amino acid sequence to porins from enterobacteria was only 22%, Nevertheless, multiple alignments of this sequence with those from several OmpC porins showed several important features conserved in the T, ferrooxidans surface protein, such as the approximate locations of 16 transmembrane beta strands, eight loops, including a large external L3 loop, and eight turns which allowed us to propose a putative 16-stranded beta-barrel porin structure for the protein. These results together with the previously known capacity of Omp40 to form ion channels in planar lipid bilayers strongly support its role as a porin in this chemolithoautotrophic acidophilic microorganism. Some characteristics of the Omp40 protein, such as the presence of a putative L3 loop with an estimated isoelectric point of 7.21 allow us to speculate that this can be the result of an adaptation of the acidophilic T. ferrooxidans to prevent free movement of protons across its outer membrane.