Zhang Yan, Gladyshev Vadim N
Department of Biochemistry, University of Nebraska, Lincoln, NE 68588-0664, USA.
J Mol Biol. 2008 Jun 13;379(4):881-99. doi: 10.1016/j.jmb.2008.03.051. Epub 2008 Apr 3.
The trace element molybdenum (Mo) is utilized in many life forms, and it is a key component of several enzymes involved in nitrogen, sulfur, and carbon metabolism. With the exception of nitrogenase, Mo is bound in proteins to a pterin, thus forming the molybdenum cofactor (Moco) at the catalytic sites of molybdoenzymes. Although a number of molybdoenzymes are well characterized structurally and functionally, evolutionary analyses of Mo utilization are limited. Here, we carried out comparative genomic and phylogenetic analyses to examine the occurrence and evolution of Mo utilization in bacteria, archaea and eukaryotes at the level of (i) Mo transport and Moco utilization trait, and (ii) Mo-dependent enzymes. Our results revealed that most prokaryotes and all higher eukaryotes utilize Mo whereas many unicellular eukaryotes including parasites and most yeasts lost the ability to use this metal. In addition, eukaryotes have fewer molybdoenzyme families than prokaryotes. Dimethylsulfoxide reductase (DMSOR) and sulfite oxidase (SO) families were the most widespread molybdoenzymes in prokaryotes and eukaryotes, respectively. A distant group of the ModABC transport system, was predicted in the hyperthermophilic archaeon Pyrobaculum. ModE-type regulation of Mo uptake occurred in less than 30% of Moco-utilizing organisms. A link between Mo and selenocysteine utilization in prokaryotes was also identified wherein the selenocysteine trait was largely a subset of the Mo trait, presumably due to formate dehydrogenase, a Mo- and selenium-containing protein. Finally, analysis of environmental conditions and organisms that do or do not depend on Mo revealed that host-associated organisms and organisms with low G+C content tend to reduce their Mo utilization. Overall, our data provide new insights into Mo utilization and show its wide occurrence, yet limited use of this metal in individual organisms in all three domains of life.
微量元素钼（Mo）在许多生命形式中都有被利用，并且它是参与氮、硫和碳代谢的几种酶的关键组成部分。除了固氮酶外，钼在蛋白质中与蝶呤结合，从而在钼酶的催化位点形成钼辅因子（Moco）。尽管许多钼酶在结构和功能上已得到充分表征，但对钼利用的进化分析却很有限。在此，我们进行了比较基因组学和系统发育分析，以在以下两个层面研究细菌、古菌和真核生物中钼利用的发生和进化：（i）钼转运和Moco利用特性，以及（ii）钼依赖性酶。我们的结果表明，大多数原核生物和所有高等真核生物都利用钼，而许多单细胞真核生物，包括寄生虫和大多数酵母，失去了使用这种金属的能力。此外，真核生物的钼酶家族比原核生物少。二甲基亚砜还原酶（DMSOR）和亚硫酸盐氧化酶（SO）家族分别是原核生物和真核生物中分布最广泛的钼酶。在嗜热古菌嗜热栖热菌中预测到了一组远缘的ModABC转运系统。在不到30%的利用Moco的生物体中发生了钼摄取的ModE型调控。还确定了原核生物中钼与硒代半胱氨酸利用之间的联系，其中硒代半胱氨酸特性在很大程度上是钼特性的一个子集，这可能是由于甲酸脱氢酶，一种含钼和硒的蛋白质。最后，对依赖或不依赖钼的环境条件和生物体的分析表明，宿主相关生物体和低G+C含量的生物体倾向于减少其钼利用。总体而言，我们的数据为钼的利用提供了新的见解，并表明其广泛存在，但在生命的所有三个域中的单个生物体中这种金属的使用有限。
