Department of Microbiology, North Carolina State University, Raleigh, NC 27695, USA.
Mol Microbiol. 2009 Nov;74(3):758-71. doi: 10.1111/j.1365-2958.2009.06901.x.
Campylobacter jejuni is an important human pathogen that causes millions of cases of food-borne enteritis each year. The C. jejuni respiratory chain is highly branched and contains at least four enzymes predicted to contain a metal binding pterin (MPT), with the metal being either molybdenum or tungsten. Also predicted are two separate transport systems, one for molybdenum encoded by modABC and a second for tungsten encoded by tupABC. Both transport systems were mutated and the activities of the four predicted MPT-containing enzymes were assayed in the presence of molybdenum and tungsten in wild-type and mod and tup backgrounds. Results indicate that mod is primarily a molybdenum transporter that can also transport tungsten, while tup is a tungsten-specific transporter. The MPT containing enzymes nitrate reductase, sulphite oxidase, and SN oxide reductase are strict molybdoenzymes while formate dehydrogenase prefers tungsten. A ModE-like protein regulates both transporters, repressing mod in the presence of both molybdenum and tungsten and tup only in the presence of tungsten. Like other ModE proteins, the C. jejuni ModE binds DNA through a helix-turn-helix DNA binding domain, but unlike other members of the ModE family it does not have a metal binding domain.
空肠弯曲菌是一种重要的人类病原体，每年导致数百万例食源性肠炎。空肠弯曲菌的呼吸链高度分支，至少包含四种预测含有金属结合蝶呤（MPT）的酶，金属要么是钼要么是钨。还预测有两个单独的运输系统，一个是由 modABC 编码的钼，另一个是由 tupABC 编码的钨。两个运输系统都发生了突变，并在野生型和 mod 和 tup 背景下，在钼和钨存在的情况下，检测了四个预测含有 MPT 的酶的活性。结果表明，mod 主要是一种钼转运蛋白，也可以转运钨，而 tup 是一种钨特异性转运蛋白。含有 MPT 的酶硝酸盐还原酶、亚硫酸盐氧化酶和 SN 氧化物还原酶是严格的钼酶，而甲酸脱氢酶则更喜欢钨。一种类似于 ModE 的蛋白调节两个转运蛋白，在钼和钨存在的情况下抑制 mod，而仅在钨存在的情况下抑制 tup。与其他 ModE 蛋白一样，空肠弯曲菌的 ModE 通过一个螺旋-转角-螺旋 DNA 结合域结合 DNA，但与 ModE 家族的其他成员不同，它没有金属结合域。
