Structural Characterization of Procaryotic Metal Reductase Systems

近年来见证了地球微生物学领域的兴起，该领域侧重于微生物过程通过矿床的形成和降解来塑造我们的环境的影响。许多以前被认为是纯无机成因的地质构造，今天被认为是原核生物代谢的产物。其中，细菌对不溶性金属氧化物（主要是Fe III和Mn IV）的还原是厌氧水生环境中一个主要的呼吸过程，在一定条件下可以氧化80%至90%的有效有机碳。由于许多金属还原细菌能够氧化芳香烃，如苯和甲苯，并且在所描述的氧化金属底物中有砷、铬和铀，因此这一过程具有进一步的生态重要性。金属还原酶活性已在一系列可溶性金属蛋白中被发现，但完整的呼吸机制由跨越细菌膜的多亚基多血红蛋白系统组成。它在细菌细胞的外部展示了实际的催化单元，在那里它们可以直接与它们的不溶性底物相互作用。

Recent years have witnessed the emergence of the field of geomicrobiology, which focusses on the influence of microbial processes on shaping our environment through the formation and degradation of mineral deposits. Many geological formations formerly believed to be of purely inorganic origin are today known to be the product of procaryotic metabolism. Herein, becterial reduction of insoluble metal oxides, predominantly of Fe III and Mn IV, is a major respiratory process in anaerobic, aquatic environments and can under certain conditions account for the oxidation of 80 to 90 % of the available organic carbon. This process gains further ecological importance by the fact that many metal-reducing bacteria are able to oxidize aromatic hydrocarbons such as benzene and toluene and that among the described oxidized metal substrates are those of arsenic, chromium and uranium. Metal reductase activity has been found in a range of soluble metalloproteins, but the complete, respiratory machinery consists of a multisubunit multiheme protein system spanning both bacterial membranes. It presents the actual catalytic units on the outside of the bacterial cells, where they can directly interact with their insoluble substrates.