Balme A, Brunt C E, Pallister R L, Chapman S K, Reid G A
Department of Chemistry, University of Edinburgh, Scotland, UK.
Biochem J. 1995 Jul 15;309 ( Pt 2)(Pt 2):601-5. doi: 10.1042/bj3090601.
Flavocytochrome b2 consists of two distinct domains. The N-terminal domain contains protohaem IX and the larger, C-terminal domain contains flavin mononucleotide (FMN). We describe here the isolation of the flavin-binding domain expressed in Escherichia coli independent of the cytochrome domain. The isolated domain is an efficient lactate dehydrogenase with ferricyanide as electron acceptor but reduces cytochrome c, the physiological oxidant for flavocytochrome b2, extremely poorly; electron transfer from the flavin-binding domain to the separately expressed cytochrome domain is undetectable. FMN reduction by lactate occurs as a single exponential process in the isolated flavin-binding domain, in contrast to the biphasic kinetics observed with native flavocytochrome b2.
黄素细胞色素b2由两个不同的结构域组成。N端结构域含有原血红素IX，而较大的C端结构域含有黄素单核苷酸（FMN）。我们在此描述了在大肠杆菌中独立于细胞色素结构域表达的黄素结合结构域的分离。分离出的结构域是一种以铁氰化物作为电子受体的高效乳酸脱氢酶，但还原细胞色素c（黄素细胞色素b2的生理氧化剂）的能力极差；从黄素结合结构域到单独表达的细胞色素结构域的电子转移无法检测到。与天然黄素细胞色素b2观察到的双相动力学相反，乳酸在分离出的黄素结合结构域中还原FMN是一个单指数过程。
