Zinc uptake, oxidative stress and the FNR-like proteins of Lactococcus lactis

Abstract

Lactococcus lactis ssp. cremoris MG1363 contains two FNR homologues, FlpA and FlpB, encoded by the distal genes of two paralogous operons (orfX(A/B)-orfY(A/B)-flpA/B). An flpA flpB double mutant strain is hypersensitive to hydrogen peroxide and has a depleted intracellular Zn(II) pool. The phenotypes of the flp mutant strains suggest that FlpA and FlpB control the expression of high and low affinity ATP-dependent Zn(II) uptake systems, respectively. Plate tests revealed that expression from a orfX(B)::lac reporter was activated by Cd(II), consistent with other Zn(II)-regulated systems. The link between a failure to acquire Zn(II) and hypersensitivity to oxidative stress suggests that Zn(II) may be required to protect vulnerable protein thiols from oxidation.

Severe Zinc Depletion of Escherichia coli

“…These data were compared with cultures treated with TPEN (Fig. 3B), which is widely used as a Zn 2ϩ chelator (3,7,32,42,43,45). Fig.…”

Cell-Wide Responses to Low-Oxygen Exposure inDesulfovibrio vulgarisHildenborough

“…Although it was highly upregulated in both conditions studied here, DVU3384 may be a general stress response candidate. Additionally, although zinc uptake regulons have been shown to increase with O 2 exposure in lactobacilli (50) and with oxidative stress in Bacillus (19), the DVU3384 protein may not be a zinc binding protein. In proteins with confirmed zinc binding motifs, such as E. coli YjaI, known to preferentially bind Zn and Ni (43), Zn binding is conferred by a two-part motif: an N-terminally located sequence, HRWH GRC, and a C-terminally located sequence, HGGHGMW.…”

Inactivation of the Lactococcus lactis high-affinity phosphate transporter confers oxygen and thiol resistance and alters metal homeostasis

“…In our mutagenesis, we did not obtain mutants affected in known or putative metal transporters (Gostick et al, 1999;Scott et al, 2000;Turner et al, 2007), nor did we obtain mutants in regulators of such transporters, e.g. ZitR and the FNRlike proteins of L. lactis (Gostick et al, 1999;Llull & Poquet, 2004;Scott et al, 2000). This might suggest that the transporters are redundant or that pst mutation has a pleiotropic role affecting intracellular availability of several metals, which would not be obtained by inactivation of a single transporter.…”

“…Interestingly, results suggestive of metal transport via phosphate uptake systems were previously reported in other species (Alvarez & Jerez, 2004;Beard et al, 2000;van Veen et al, 1994van Veen et al, , 1993, and could explain the resistance to metal toxicity. In our mutagenesis, we did not obtain mutants affected in known or putative metal transporters (Gostick et al, 1999;Scott et al, 2000;Turner et al, 2007), nor did we obtain mutants in regulators of such transporters, e.g. ZitR and the FNRlike proteins of L. lactis (Gostick et al, 1999;Llull & Poquet, 2004;Scott et al, 2000).…”