Studies on Mechanism of Biomagnetite Synthesis in the cell

1.规模化培养趋磁菌--磁螺菌。通过对培养基中氧气浓度等生长条件的考察，探索出规模化培养趋磁细菌--磁性螺杆菌的方法。因此，我们可以得到1.3g(湿重)。10 L培养液中的细胞。2.趋磁细菌--磁性螺杆菌呼吸链成分的纯化及性质。C型和CDL型细胞色素已从细菌中纯化到电泳均一状态。细胞色素C-550具有与光合细菌C型细胞色素几乎相同的光谱性质和分子特征。此外，细胞色素c铁与膜一起被迅速氧化。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含有血红素c和h…分子中有更多的EME d1。Cnzyme显示出较高的亚硝酸还原酶活性，但生理电子供体尚未在本研究中阐明。另一方面，我们从嗜磁细菌中提纯了一种新的血红蛋白--磁性螺杆菌。虽然与细胞膜紧密结合的血红蛋白表现出与细胞色素A1非常相似的特殊性质。该蛋白不含血红素a分子，经高效液相色谱和原子吸收光谱检测到两种新类型的血红素，且该蛋白几乎不具有细胞色素C氧化酶活性。因此，该血红素蛋白似乎不可能在活体内起到末端氧化酶的作用。3.趋磁细菌MagnetSpirillum Magnetotacticum Fe(III)-还原酶的纯化。我们对趋磁细菌Magnetspirillun Magnetotacticum的可溶性部分所特有的Fe(III)-还原酶进行了纯化。该酶的相对分子质量为51000，具有较高的NADH-Fe(III)氧化还原酶活性，Km值为4µM，Vmax为170nmol/min/mg蛋白。现在我们研究了Fe(III)还原酶在磁铁矿生物合成中的生理功能。较少

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