好酸性鉄酸化細菌 Acidithiobacillus ferrooxidans の染色体凝集・分配タンパク質（ScpB）の性質

　Acidithiobacillus ferrooxidans is one of the most widely used microorganisms in bioleaching operations to recover copper from low-grade copper sulfide. This bacterium uses ferrous iron and reduced inorganic sulfur compounds (RISCs) as energy sources. Transcriptions of genes thought to be involved in the oxidation of RISCs have been known to be highly activated in A. ferrooxidans cells grown on RISCs, while transcriptions of genes involved in the iron oxidation were repressed in the cells grown on RISCs. A gene encoding a putative chromosome segregation and condensation protein (ScpB) with a helix-turn-helix motif was found in the upstream region of sulfide : quinone oxidoreductase gene, whose expression was up-regulated in cells grown in sulfur and tetrathionate. A semi-quantitative PCR analysis using cDNA prepared from iron-, sulfur-, or tetrathionate-grown cells revealed that the transcription of scpB was up-regulated in cells grown on sulfur or tetrathionate as the energy source. Electrophoretic mobility shift assays were employed to examine whether the ScpB functions as a transcription factor. The result indicated that the recombinant His-tagged ScpB protein was able to nonspecifically bind in vitro to DNA. This is the first report on a direct association of ScpB with DNA.　Acidithiobacillus ferrooxidans は，低品位の銅鉱石から銅を回収するバイオリーチングにおいて使用される微生物 の一つである．この細菌は，エネルギー源として二価鉄イオンや還元型無機硫黄化合物（RISC）を使用する．鉄の酸化に関与する遺伝子の転写は，A. ferrooxidans が RISC で生育したときには抑制されるが，RISC の酸化に関与すると考えられている遺伝子の転写は活性化されることが知られている．硫黄やテトラチオン酸で生育したときにその発現が上方制御される硫化水素：キノン酸化還元酵素のすぐ上流に，ヘリックスターンへリックスモティーフを持つ，ScpB と推定されるタンパク質をコードする遺伝子が存在していた．鉄，硫黄，テトラチオン酸生育細胞から調製した cDNA を用いた半定量的 PCR 分析の結果，硫黄やテトラチオン酸で生育した細胞内の scpB 遺伝子の転写は，鉄生育細胞と比較すると上方制御されていた．組換え ScpB タンパク質を用いたゲルシフトアッセイ法で，ScpB が転写制御因子として機能するかどうかを調べた．その結果，ScpB は DNA に結合したが，結合の特異性はなかった．ScpB が直接 DNA と相互作用する報告はこれまでになかった

好酸性鉄酸化細菌 Acidithiobacillus ferrooxidans の染色体凝集・分配タンパク質（ScpB）の性質

　Acidithiobacillus ferrooxidans is one of the most widely used microorganisms in bioleaching operations to recover copper from low-grade copper sulfide. This bacterium uses ferrous iron and reduced inorganic sulfur compounds (RISCs) as energy sources. Transcriptions of genes thought to be involved in the oxidation of RISCs have been known to be highly activated in A. ferrooxidans cells grown on RISCs, while transcriptions of genes involved in the iron oxidation were repressed in the cells grown on RISCs. A gene encoding a putative chromosome segregation and condensation protein (ScpB) with a helix-turn-helix motif was found in the upstream region of sulfide : quinone oxidoreductase gene, whose expression was up-regulated in cells grown in sulfur and tetrathionate. A semi-quantitative PCR analysis using cDNA prepared from iron-, sulfur-, or tetrathionate-grown cells revealed that the transcription of scpB was up-regulated in cells grown on sulfur or tetrathionate as the energy source. Electrophoretic mobility shift assays were employed to examine whether the ScpB functions as a transcription factor. The result indicated that the recombinant His-tagged ScpB protein was able to nonspecifically bind in vitro to DNA. This is the first report on a direct association of ScpB with DNA.　Acidithiobacillus ferrooxidans は，低品位の銅鉱石から銅を回収するバイオリーチングにおいて使用される微生物 の一つである．この細菌は，エネルギー源として二価鉄イオンや還元型無機硫黄化合物（RISC）を使用する．鉄の酸化に関与する遺伝子の転写は，A. ferrooxidans が RISC で生育したときには抑制されるが，RISC の酸化に関与すると考えられている遺伝子の転写は活性化されることが知られている．硫黄やテトラチオン酸で生育したときにその発現が上方制御される硫化水素：キノン酸化還元酵素のすぐ上流に，ヘリックスターンへリックスモティーフを持つ，ScpB と推定されるタンパク質をコードする遺伝子が存在していた．鉄，硫黄，テトラチオン酸生育細胞から調製した cDNA を用いた半定量的 PCR 分析の結果，硫黄やテトラチオン酸で生育した細胞内の scpB 遺伝子の転写は，鉄生育細胞と比較すると上方制御されていた．組換え ScpB タンパク質を用いたゲルシフトアッセイ法で，ScpB が転写制御因子として機能するかどうかを調べた．その結果，ScpB は DNA に結合したが，結合の特異性はなかった．ScpB が直接 DNA と相互作用する報告はこれまでになかった

Characterization of an OmpA-like outer membrane protein of the acidophilic iron-oxidizing bacterium, Acidithiobacillus ferrooxidans

An OmpA family protein (FopA) previously reported as one of the major outer membrane proteins of an acidophilic iron-oxidizing bacterium Acidithiobacillus ferrooxidans was characterized with emphasis on the modification by heat and the interaction with peptidoglycan. A 30-kDa band corresponding to the FopA protein was detected in outer membrane proteins extracted at 75°C or heated to 100°C for 10 min prior to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). However, the band was not detected in outer membrane proteins extracted at ≤40°C and without boiling prior to electrophoresis. By Western blot analysis using the polyclonal antibody against the recombinant FopA, FopA was detected as bands with apparent molecular masses of 30 and 90 kDa, suggesting that FopA existed as an oligomeric form in the outer membrane of A. ferrooxidans. Although the fopA gene with a sequence encoding the signal peptide was successfully expressed in the outer membrane of Escherichia coli, the recombinant FopA existed as a monomer in the outer membrane of E. coli. FopA was detected in peptidoglycan-associated proteins from A. ferrooxidans. The recombinant FopA also showed the peptidoglycan-binding activity