Zientz E, Six S, Unden G
Institut für Mikrobiologie und Weinforschung, Johannes Gutenberg-Universitat Mainz, Federal Republic of Germany.
J Bacteriol. 1996 Dec;178(24):7241-7. doi: 10.1128/jb.178.24.7241-7247.1996.
In Escherichia coli, two carriers (DcuA and DcuB) for the transport of C4 dicarboxylates in anaerobic growth were known. Here a novel gene dcuC was identified encoding a secondary carrier (DcuC) for C4 dicarboxylates which is functional in anaerobic growth. The dcuC gene is located at min 14.1 of the E. coli map in the counterclockwise orientation. The dcuC gene combines two open reading frames found in other strains of E. coli K-12. The gene product (DcuC) is responsible for the transport of C4 dicarboxylates in DcuA-DcuB-deficient cells. The triple mutant (dcuA dcuB dcuC) is completely devoid of C4-dicarboxylate transport (exchange and uptake) during anaerobic growth, and the bacteria are no longer capable of growth by fumarate respiration. DcuC, however, is not required for C4-dicarboxylate uptake in aerobic growth. The dcuC gene encodes a putative protein of 461 amino acid residues with properties typical for secondary procaryotic carriers. DcuC shows sequence similarity to the two major anaerobic C4-dicarboxylate carriers DcuA and DcuB. Mutants producing only DcuA, DcuB, or DcuC were prepared. In the mutants, DcuA, DcuB, and DcuC were each able to operate in the exchange and uptake mode.
在大肠杆菌中，已知有两种载体（DcuA和DcuB）在厌氧生长过程中负责转运C4二羧酸。在此，鉴定出一个新基因dcuC，它编码一种用于C4二羧酸的次级载体（DcuC），该载体在厌氧生长中发挥功能。dcuC基因位于大肠杆菌染色体图谱的14.1分钟处，呈逆时针方向。dcuC基因由在其他大肠杆菌K - 12菌株中发现的两个开放阅读框组成。该基因产物（DcuC）负责在缺乏DcuA - DcuB的细胞中转运C4二羧酸。三重突变体（dcuA dcuB dcuC）在厌氧生长期间完全缺乏C4二羧酸的转运（交换和摄取），并且细菌不再能够通过富马酸呼吸进行生长。然而，在有氧生长中摄取C4二羧酸并不需要DcuC。dcuC基因编码一个推定的含有461个氨基酸残基的蛋白质，具有原核生物次级载体的典型特性。DcuC与两种主要的厌氧C4二羧酸载体DcuA和DcuB具有序列相似性。制备了仅产生DcuA、DcuB或DcuC的突变体。在这些突变体中，DcuA、DcuB和DcuC各自都能够以交换和摄取模式发挥作用。
