Metal Ion Homeostasis in Bacillus subtilis

描述（由申请人提供）：本研究的长期目标是了解细菌细胞如何维持金属离子稳态。必需的金属离子必须从环境中获得，运输到细胞内，并运输到正确的细胞内目的地。当金属离子受限时，诱导高亲和力摄取机制。当过量时，细胞诱导外排、解毒或储存机制的合成。从宿主获得足够的金属离子的能力对细菌病原体至关重要，金属摄取系统在体内高度表达，表面暴露的运输蛋白通常是宿主免疫反应的目标。金属离子稳态紊乱也是人类疾病的主要原因，包括贫血、Menkes病和Wilson病以及其他一些神经退行性疾病。

DESCRIPTION (provided by applicant): The long-term objective of this research is to understand how bacterial cells maintain metal ion homeostasis. Essential metal ions must be obtained from the environment, transported into the cell, and trafficked to the correct intracellular destinations. When metal ions are limiting, high affinity uptake mechanisms are induced. When in excess, the cell induces the synthesis of efflux, detoxication, or storage mechanisms. The ability to obtain sufficient metal ions from the host is crucial to bacterial pathogens, metal uptake systems are highly expressed in vivo, and surface-exposed transport proteins are often targets for the host immune response. Disorders of metal ion homeostasis are also a major cause of human disease including anemias, Menkes', and Wilson's diseases, and several other neurodegenerative diseases. The genetic responses to changes in metal ion availability are coordinated by metalloregulatory proteins. In the Gram-positive bacterium Bacillus subtilis metal-specific regulators control the uptake of Mn (MntR), Fe (Fur), and Zn (Zur), and others regulate efflux mechanisms induced when metal ions are in excess (CueR, CzrA, ArsR, YdeT). We will measure the metal ion content and quotas needed for growth for both wild-type and mutants altered in metal ion homeostasis. We will test the hypothesis that adsorption of metal ions to the cell wall plays a role in both uptake and storage of metals and we will characterize pathways for Fe and Zn uptake. We will test the hypotheses that MrgA and Dps function in Fe storage and detoxification and that Zn-containing ribosomal proteins provide a major intracellular Zn store that can be mobilized under Zn limitation. Genetic and biochemical approaches will be used to further our understanding of metal-sensing by MntR, Fur, Zur, CueR, and ArsR family members by site-directed mutagenesis of metal ligands, in vivo analyses of altered function mutants, and structure-determination methods.