Molecular genetics of a chromosomal locus involved in copper tolerance in Escherichia coli K‐12

Abstract

The cutA locus, presumably involved in copper tolerance in Escherichia coli, was characterized by a mutation leading to copper sensitivity. Copper-accumulation measurements with radioactive 64Cu2+ showed increased uptake by cutA copper-sensitive mutant cells, and reduced uptake when the cutA mutation was complemented in trans. The locus was mapped using complementation of the cutA mutant to partial copper tolerance with wild-type chromosomal fragments. The 3.2 kb DNA region involved in cutA was sequenced and analysed, revealing three significant open reading frames, none of which had been previously published. The products of all three open reading frames were identified, when synthesized with the T7 phage promoter expression system, as polypeptides of about 50 kDa, 24 kDa, and 13 kDa, consistent with the sizes predicted from the DNA sequences. The 50 kDa and 24 kDa polypeptides were found in the bacterial inner membrane, and the 13 kDa polypeptide with the cytoplasmic fraction. In addition to being required for copper tolerance, cutA affects tolerance levels to zinc, nickel, cobalt and cadmium salts. Transcriptional fusions of cutA with the lux operon showed induction by copper, zinc, nickel, cobalt and, to a lesser extent, cadmium, manganese and silver salts.

Transcriptional Activation of an Escherichia coliCopper Efflux Regulon by the Chromosomal MerR Homologue, CueR

“…Numerous attempts have been made to identify the genes involved in controlling copper levels in E. coli; however, few of these genes have been directly linked to copper metabolism, transport, or regulation (5,6). For instance, the nlpE (cutF) gene, which encodes for a novel lipoprotein, and dipZ (cutA2), which encodes for a disulfide isomerase, have indirect connections with copper metabolism (6,7).…”

CutA Divalent Cation Tolerance Homolog (Escherichia coli) (CUTA) Regulates β-Cleavage of β-Amyloid Precursor Protein (APP) through Interacting with β-Site APP Cleaving Protein 1 (BACE1)

“…Some studies have suggested that CUTA may play roles in copper tolerance/toxicity (20,40), AChE activity (18), signal transduction (21), etc. However, so far the exact functions of CUTA, especially those of human CUTA, remain largely undetermined.…”

“…The trimeric core is preceded by a region of variable length with several variants in mammals (19). In bacteria, CutA is involved in copper tolerance, and some mutations in the cutA gene lead to copper sensitivity due to its increased uptake (20). Additional studies showed that many CutA proteins have a copper binding capacity and that copper could induce reversible aggregation of the CutA protein (21,22).…”

Construction of a High-Resolution 2.5-Mb Transcript Map of the Human 6p21.2–6p21.3 Region Immediately Centromeric of the Major Histocompatibility Complex

“…2C), which is conserved across species from different taxa. In Escherichia coli the CutA protein is presumably involved in copper tolerance and also affects tolerance to zinc, cadmium, nickel, and cobalt salts (Fong et al 1995). A putative CpG island was identified on the 5Ј end of ntcon6.…”

“…The encoded peptide showed similarity to the Arabidopsis thaliana CutA protein (Fong et al 1995; Fig. 2C), which is conserved across species from different taxa.…”