Copper trafficking in the CsoR regulon of Streptomyces lividans

Abstract

In the actinobacterium Streptomyces lividans copper homeostasis is controlled through the action of the metalloregulator CsoR. Under copper stress, cuprous ions bind to apo-CsoR resulting in the transcriptional derepression of genes encoding for copper efflux systems involving CopZ-like copper chaperones and CopA-like P-type ATPases. Whether CsoR obtains copper via a protein-protein mediated trafficking mechanism is unknown. In this study we have characterised the copper trafficking properties of two S. lividans CopZ proteins (SLI_1317 and SLI_3079) under the transcriptional control of a CsoR (SLI_4375). Our findings indicate that both CopZ-proteins have cysteine residues in the Cu(i) binding MX1CX2X3C motif with acid-base properties that are modulated for a high cuprous ion affinity and favourable Cu(i)-exchange with a target. Using electrophoretic mobility shift assays transfer of Cu(i) is shown to occur in a unidirectional manner from the CopZ to the CsoR. This transfer proceeds via a shallow thermodynamic affinity gradient and is also kinetically favoured through the modulation of the acid-base properties of the cysteine residues in the Cys2His cuprous ion binding motif of CsoR. Using RNA-seq coupled with the mechanistic insights of Cu(i) transfer between CopZ and CsoR in vitro, we propose a copper trafficking pathway for the CsoR regulon that initially involves the buffering of cytosolic copper by three CopZ chaperones followed by transfer of Cu(i) to CsoR to illicit a transcriptional response.

A two-component system gene SACE_0101 regulates copper homeostasis in Saccharopolyspora erythraea

“…To maintain the copper homeostasis, cytosolic copper is precisely regulated by resistance proteins. The twocomponent system was previously confirmed as the key regulatory system for the extra-cytoplasmic sensing of elevated copper ion and can regulate the expression of related genes to elicit adaptive responses to changes in the concentration of copper (Chaplin et al 2015;Singh et al 2014). Here, we found a total of 8 genes in the genome of S. erythraea NRRL23338 that are potentially involved in copper metabolism.…”

The interplay of the metallosensor CueR with two distinct CopZ chaperones defines copper homeostasis in Pseudomonas aeruginosa

“…1B). This His is likely responsible for the higher Cu ϩ affinity observed in P. aeruginosa CopZ2 (15), as it has been shown that its removal decreases S. lividans CopZs affinity for Cu ϩ (25). Moreover, the His is probably determinant of their different behavior in the presence of Cu ϩ where CopZ2 (but not CopZ1) forms Cu ϩ -mediated multimeric structures even with equimolar Cu ϩ as observed in native PAGE gels (Fig.…”

“…Both are under control of CueR, binding Cu ϩ with 1:1 stoichiometry and high affinity, CopZ1 4 ϫ 10 Ϫ15 M and CopZ2 8 ϫ 10 Ϫ17 M (15). This multiplicity of copper chaperones has been also observed in Streptomyces lividans that has four CopZ-like Cu ϩ chaperones (25). Even though their Cu ϩ affinities have been determined (CopZ-1317 10 Ϫ17 M and CopZ-3079 10 Ϫ18 M), their possible function is obscure as they both appear to interact similarly with CsoR.…”

“…Quite relevant, it is unknown how CueR acquires the metal. Although CopZ-like Cu ϩ chaperones appear to deliver the metal to other transcriptional regulators such as CopY (22)(23)(24) and CsoR (25). Interestingly, P. aeruginosa genome encodes for two cytoplasmic Cu ϩ chaperones, CopZ1 and CopZ2 (15).…”

Copper resistance and its regulation in the sulfate-reducing bacterium Desulfosporosinus sp. OT

“…In the absence of copper, two CsoR tetramers clutch the operator region to prevent transcription On: Fri, 11 May 2018 06:47:07 (Chaplin et al, 2015). For induction of transcription by copper, four Cu + per homotetramer bind cooperatively to a C and an H residue on one subunit and a C residue of the adjacent subunit (Jacobs et al, 2015).…”