Metal Ion Uptake and Oxidative Stress

Andrew F. Herbig; John D. Helmann

doi:10.1128/9781555817992.ch29

Chapter 29 : Metal Ion Uptake and Oxidative Stress

Authors: Andrew F. Herbig, John D. Helmann

Content Type: Monograph

Publication Year: 2002

Category: Bacterial Pathogenesis

Book DOI: 10.1128/9781555817992

Chapter DOI: 10.1128/9781555817992.ch29

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Abstract:

In several systems, it is now clear that oxidative stress responses are intimately and reciprocally connected with systems to transport and store metal ions. Regardless, it is clear that one has much to learn about metal ion uptake into and within cells and how these processes affect, and are affected by, oxidative stress. This chapter provides an overview of metalloregulation in Bacillus subtilis, identifies the links between metal ion homeostasis and oxidative stress responses, and draws comparisons with homologous or analogous systems in other organisms. Bacteria overcome iron limitation by secreting iron-chelating agents, called siderophores, into their environment and then transporting the ferri-siderophore complex to assimilate the captured iron. Per boxes are found near oxidative stress genes, including catalase in Listeria seeligeri and ahp operons from Enterococcusfaecalis and Clostridiumpasteurianum. Campylobacter jejuni has two Fur homologs, Fur and PerR, which regulate iron uptake and oxidative stress genes, respectively. A study on the identification of two metalloregulated lacZ fusions that responded differently to added metal ions was conducted and these regulators were identified by eventually engineering mutations of four candidate metalloregulators found by genome sequencing. This work led to the characterization of the Fur, PerR, Zur, and MntR systems. Homologs of each of these regulators have been found in several other bacteria. S. aureus, like B. subtilis, has three Fur homologs that appear to correspond to Fur, PerR, and Zur. Since Fur, PerR, and MntR respond to an overlapping set of metal ions in vivo, these regulons are intimately interconnected.

Citation: Herbig A, Helmann J. 2002. Metal Ion Uptake and Oxidative Stress, p 405-414. In Sonenshein A, Losick R, Hoch J (ed), Bacillus subtilis and Its Closest Relatives. ASM Press, Washington, DC. doi: 10.1128/9781555817992.ch29

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Metal Ion Uptake and Oxidative Stress

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FIGURE 1

Multiple sequence alignment of Fur family members. The three Fur homologs from Β. subtilis (Zur, PerR, and Fur) are compared to close homologs. B. subtilis Fur (BsuFur) is functionally and structurally similar to E. coli Fur (EcoFur), PerR is aligned to a homolog from Streptococcus pyogenes (SpyPerR), and Zur (BsuZur) is aligned to a homolog from Staphyhcoccus epidermidis (SepFur). Regions thought to function in DNA binding and metal ion binding are annotated. Reprinted from reference 15 with permission.

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FIGURE 1

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FIGURE 2

Sequence alignment of MntR-like repressors with DtxR. MntR and selected homologs are aligned with each other and with DtxR (Cdi). All the repressors have an amino-terminal DNA-binding domain of about 73 amino acids (first two lines of the alignment). The DNA-binding recognition helix is indicated. The carboxyl-terminal metal binding domain contains two metal ion binding sites: the proposed primary site (site 2) for binding of regulatory ligand (indicated by ·) is an octahedral site containing DtxR Cysl02(Aspl02), Glul05 and Hisl06, MetlO, a main chain carbonyl (D120), and a water ( 30 ). Binding site 1 (indicated by o) binds a cation-anion pair ( 72 , 75 ), although the role of this binding in regulation has not been established. Protein sequences are from B. subtilis (Bsu), Corynebacterium diphtheriae (Cdi), Staphylococcus epidermidis (Sep), E. coli (Eco), Methanococcus jannaschii (Mja), and Treponema pallidum (Tpa). Only the first two domains of the Cdi DtxR protein are included. The third SH3-like domain, connected to the first two by a flexible linker (GNSDAAA), is poorly structured ( 75 ) and is not found in MntR family members. Reprinted from Que and Helmann ( 76 ) with permission.

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FIGURE 2

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FIGURE 3

Relationships between the Fur, PerR, and MntR regulons. Fur and MntR act to regulate intracellular iron and manganese levels, respectively. PerR binds either Mn(II) or Fe(II) to repress expression of the peroxide stress response. Alterations in metal ion homeostasis are proposed to affect the distribution of PerR between two nonequivalent forms, PerR-Fe and PerR-Mn. These forms appear to differ both in DNA-binding selectivity and in reactivity with H2O2 (see text for details).

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FIGURE 3

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Tables

Metal Ion Uptake and Oxidative Stress

/content/10.1128/9781555817992.chap29.tab29-1

TABLE 1

Characterized metalloregulatory systems in Bacillus subtilis and functional homologs in other gram-positive organisms

a In some cases, only a subset of known targets is listed, and only the first gene in each operon is listed.

10.1128/9781555817992/tab29-1_thmb.gif

10.1128/9781555817992/tab29-1.gif

TABLE 1

Characterized metalloregulatory systems in Bacillus subtilis and functional homologs in other gram-positive organisms

a In some cases, only a subset of known targets is listed, and only the first gene in each operon is listed.

/content/10.1128/9781555817992.chap29.tab29-2

TABLE 2

Known and putative Fur box sequences in B. subtilis

a Position of 3' Fur box base to first base in start codon of gene.

b Dashes represent bases identical to consensus.

c Divergent gene orientations.

d Part of the Per regulon ( 48 ).

e Numbers in parentheses indicate multiple Fur boxes.

f N.D., not determined.

10.1128/9781555817992/tab29-2_thmb.gif

10.1128/9781555817992/tab29-2.gif

TABLE 2

Known and putative Fur box sequences in B. subtilis

a Position of 3' Fur box base to first base in start codon of gene.

b Dashes represent bases identical to consensus.

c Divergent gene orientations.

d Part of the Per regulon ( 48 ).

e Numbers in parentheses indicate multiple Fur boxes.

f N.D., not determined.

/content/10.1128/9781555817992.chap29.tab29-3

TABLE 3

Documented Per boxes in B. subtilis

a Base pairs from start codon.

b Numbers in parentheses indicate the presence of multiple Per boxes.

c Dashes represent bases matching consensus.

10.1128/9781555817992/tab29-3_thmb.gif

10.1128/9781555817992/tab29-3.gif

TABLE 3

Documented Per boxes in B. subtilis

a Base pairs from start codon.

b Numbers in parentheses indicate the presence of multiple Per boxes.

c Dashes represent bases matching consensus.

/content/10.1128/9781555817992.chap29.tab29-4

TABLE 4

merR and arsR homologs in the B. subtilis genome

a See text for references.

10.1128/9781555817992/tab29-4_thmb.gif

10.1128/9781555817992/tab29-4.gif

TABLE 4

merR and arsR homologs in the B. subtilis genome

a See text for references.