Studies on Mechanism of Biomagnetite Synthesis in the cell

1.趋磁菌的大规模培养。通过对培养基中氧浓度等生长条件的研究，探索了趋磁菌（Magnetospirillum magnetotacticum）的大规模培养方法。因此，我们可以从10 L培养基中获得1.3g（湿wt.）细胞。趋磁螺旋菌（Magnetospirillum magnetotacticum）呼吸链成分的纯化与表征。c型和cdl型细胞色素已从细菌中纯化到电泳均匀状态。细胞色素c-550表现出与光合细菌c型细胞色素几乎相同的光谱特性和分子特征。此外，铁细胞色素c被膜迅速氧化。这些结果表明细胞色素c-550可能是呼吸链末端氧化酶的电子供体。细胞色素cd1分子中含有血红素c和血红素d1。该酶表现出较高的亚硝酸盐还原酶活性，尽管本研究尚未阐明其生理电子供体。另一方面，我们从趋磁细菌——趋磁螺旋菌中纯化了一种新的血红蛋白。虽然与细胞膜紧密结合的血红蛋白表现出与细胞色素a1非常相似的光谱特性。通过高效液相色谱法和FAB法在血红蛋白中检测到两种新的血红素。此外，血红蛋白几乎没有细胞色素c氧化酶活性。因此，血红蛋白在体内似乎不太可能起终末氧化酶的作用。趋磁菌中铁（III）还原酶的纯化本文试图从趋磁菌Magnetospirillun magnetotacticum制备的可溶性部分中纯化铁(III)-还原酶。分子量为51000的酶具有较高的NADH-Fe（III）氧化还原酶活性；Km值和Vmax分别为4muM和170 nmol/min/mg蛋白。本文研究了铁（III）还原酶在磁铁矿生物合成中的生理功能。少

1.Large scale cultivation of magnetotactic bacterium, Magnetospirillum magnetotacticum. We have tried to develop the method of large scale cultivation of magnetotactic bacterium, Magnetospirillum magnetotacticum by investigating the growth conditions such as oxygen concentration in the medium. Consequently, we could obtain 1.3g (wet wt.) cells from 10 L medium.2.Purification and characterization of the components in the respiratory chain of magnetotactic bacterium, Magnetospirillum magnetotacticum. C-type and cdl-type cytochromes have been purified from the bacterium to an electrophoretically homogeneous state. Cytochrome c-550 showed almost the same spectral properties and molecular features as those of c type cytochromes of photosynthetic bacterium. Further, the ferrocytochrome c was rapidly oxidized with the membrane. These results suggest that cytochrome c-550 may function as the electron donor for the terminal oxidase in the respiratory chain. Cytochrome cd1 contained heme c and h … More eme d1 in the molecule. The cnzyme showed high nitrite -reduc-tase activity, although the physiological electron donor has not been elucidated in this study. On the other hand, we have purifed a novel hemoprotein from mangnetotactic bacterium, Magnetospirillum magnetotacticum. Although the hemoprotein which was tightly bound with the membrane showed very similar specral properties to those of "cytochrome a1". the protein contained no molecules of heme a. Two novel types of heme were detected in the hemoprotein by HPLC and FAB.Further, the hemoprotein hardly showed cytochrome c oxidase activity. Therefore, it seems unlikely thate the hemoprotein functions as the terminal oxidase in vivo.3.Purification of Fe(III)-reductase from magnetotactic bacterium, Magnetospirillum magnetotacticum. We have tried to purify Fe(III)-reductase which was specifically found in the soluble fraction prepared from magnetotactic bacterium, Magnetospirillun magnetotacticum. The enzyme with the molecular weight of 51000 shows high NADH-Fe(III) oxidoreductase activity ; Km value and Vmax were 4muM and 170 nmol/min/mg protein, respectively. Now we have investigated the physiological function of Fe(III) reductase in the biosynthesis of magnetites. Less