Tellurite enters Escherichia coli mainly through the PitA phosphate transporter

Abstract

Several transporters suspected to be involved in tellurite uptake in Escherichia coli were analyzed. Results showed that the PitA phosphate transporter was related to tellurite uptake. Escherichia coli ΔpitA was approximately four-fold more tolerant to tellurite, and cell viability remained almost unchanged during prolonged exposure to the toxicant as compared with wild type or ΔpitB cells. Notably, reduced thiols (toxicant targets) as well as superoxide dismutase, catalase, and fumarase C activities did not change when exposing the ΔpitA strain to tellurite, suggesting that tellurite-triggered oxidative damage is attenuated in the absence of PitA. After toxicant exposure, remaining extracellular tellurite was higher in E. coli ΔpitA than in control cells. Whereas inductively coupled plasma atomic emission spectrometric studies confirmed that E. coli ΔpitA accumulates ∼50% less tellurite than the other strains under study, tellurite strongly inhibited 32Pi uptake suggesting that the PitA transporter is one of the main responsible for tellurite uptake in this bacterium.

On the role of a specific insert in acetate permeases (ActP) for tellurite uptake in bacteria: Functional and structural studies

“…These findings were subsequently confirmed[21] and it was concluded that tellurite is transported into cells of E. coli via a phosphate transport system, EcPitA. Recently, a more detailed analysis of tellurite transport in E. coli concluded that the EcPitA system has indeed a relevant role at longer exposures to With a role of acetate permeases involved in the bacterial transport of tellurite now established, in the present work we have functionally and structurally identified two types of ActPs, RcActP1 and RcActP2, assigning to the latter the bulk of transport of tellurite inside the cells.…”

“…The uptake of tellurite by the two carriers PitA and ActP2 is inhibited by the physiological substrates phosphate and acetate, respectively [18,21]. By using the two competitor substrates, it should be possible to determine the contribution of the two carriers when are simultaneously present in E. coli.…”

“…Very recently, this residual component of tellurite uptake in E. coli has been attributed to the ActP permease [22], thus requiring a reconsideration of the previous dismissal of such a role for the ActP of E. coli [21]. The expression of RcActP2 in E.…”

“…In E. coli, tellurite uptake is mostly mediated by the phosphate transport system PitAB, because a pitA deletion mutant shows only a residual tellurite uptake [21].…”

“…coli has been shown to take up tellurite via a phosphate transport system (PitA) with TeO 3 2-inhibiting the uptake of 32 P i [21]. To determine the actual tellurite uptake activity induced by RcActP2 in the host strain, the E. coli ΔpitA mutant JW3460 [23] was transformed with R. capsulatus actP2.…”