Reid R T, Live D H, Faulkner D J, Butler A
Department of Chemistry, University of California, Santa Barbara 93106-6090.
Nature. 1993 Dec 2;366(6454):455-8. doi: 10.1038/366455a0.
Virtually all microorganisms require iron for growth. The paucity of iron in surface ocean water (approximately 0.02-1.0 nM (refs 1, 2)) has spurred a lively debate concerning iron limitation of primary productivity, yet little is known about the molecular mechanisms used by marine microorganisms to sequester iron. Terrestrial bacteria use a siderophore-mediated ferric uptake system. A siderophore is a low-molecular-mass compound with a high affinity for ferric ion which is secreted by microorganisms is response to low-iron environments; siderophore biosynthesis is regulated by iron levels, with repression by high iron. Although open-ocean marine microorganisms (such as phytoplankton and bacteria) produce siderophores, the nature of these siderophores has not been investigated. We report here the first structure determination, to our knowledge, of the siderophores from an open-ocean bacterium, alterobactin A and B from Alteromonas luteoviolacea. A. luteoviolacea is found in oligotrophic and coastal waters. Alterobactin A has an exceptionally high affinity constant for ferric ion. We suggest that at least some marine microorganisms may have developed higher-affinity iron chelators as part of an efficient iron-uptake mechanism which is more effective than that of their terrestrial counterparts.
几乎所有微生物的生长都需要铁。海洋表层水中铁含量稀少（约0.02 - 1.0纳摩尔，参考文献1、2），这引发了一场关于铁对初级生产力限制的激烈争论，但对于海洋微生物用于螯合铁的分子机制却知之甚少。陆生细菌利用一种铁载体介导的铁摄取系统。铁载体是一种对铁离子具有高亲和力的低分子量化合物，由微生物在低铁环境下分泌；铁载体的生物合成受铁水平调节，高铁时受到抑制。尽管大洋中的海洋微生物（如浮游植物和细菌）会产生铁载体，但这些铁载体的性质尚未得到研究。据我们所知，我们在此首次报道了一种大洋细菌——紫色色杆菌（Alteromonas luteoviolacea）产生的铁载体——交替菌素A和B的结构测定。紫色色杆菌存在于贫营养和沿海水域。交替菌素A对铁离子具有异常高的亲和常数。我们认为，至少一些海洋微生物可能已经进化出了亲和力更高的铁螯合剂，作为一种比陆生微生物更有效的高效铁摄取机制的一部分。
