A four-subunit cytochrome bc₁ complex complements the respiratory chain of Thermus thermophilus

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• 作者：Mooser ; Daniela ; Maneg ; Oliver ; Corvey ; Carsten ; Steiner ; Thomas ; Malatesta ; Francesco ; Karas ; Michael ; et. al.
• 关键词：Thermus thermophilus ; Respiratory chain ; Cytochrome bc₁ ; Complex III ; Electron transfer ; Stopped flow kinetics
• 刊名：BBA - Bioenergetics
• 出版年：2005
• 期刊代码：13_00052728
• 类别：bio
• 出版时间：June 30, 2005
• 卷：1708
• 期：2
• 页码：262-274
• 文件大小：901 K

摘要

Several components of the respiratory chain of the eubacterium Thermus thermophilus have previously been characterized to various extent, while no conclusive evidence for a cytochrome bc₁ complex has been obtained. Here, we show that four consecutive genes encoding cytochrome bc₁ subunits are organized in an operon-like structure termed fbcCXFB. The four gene products are identified as genuine subunits of a cytochrome bc₁ complex isolated from membranes of T. thermophilus. While both the cytochrome b and the FeS subunit show typical features of canonical subunits of this respiratory complex, a further membrane-integral component (FbcX) of so far unknown function copurifies as a subunit of this complex. The cytochrome c₁ carries an extensive N-terminal hydrophilic domain, followed by a hydrophobic, presumably membrane-embedded helical region and a typical heme c binding domain. This latter sequence has been expressed in Escherichia coli, and in vitro shown to be a kinetically competent electron donor to cytochrome c₅₅₂, mediating electron transfer to the ba₃ oxidase. Identification of this cytochrome bc₁ complex bridges the gap between the previously reported NADH oxidation activities and terminal oxidases, thus, defining all components of a minimal, mitochondrial-type electron transfer chain in this evolutionary ancient thermophile.