Identity of a Plasmodium lactate/H+ symporter structurally unrelated to human transporters

Wu, Binghua; Rambow, Janis; Bock, Sinja; Holm-Bertelsen, Julia; Wiechert, Marie; Soares, Alexandra Blancke; Spielmann, Tobias; Beitz, Eric

doi:10.1038/ncomms7284

Cited by 68 publications

(165 citation statements)

References 40 publications

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“…To detect not only the electrogenic anion transport of FocA and PfFNT but additionally capture the transport of the neutral acid substrate species, we used radiolabeled substrates in our assays. 3,7 Strikingly and contrary to the electrophysiology studies, we observed increasing transport rates with increasing acidity of the assay media. Apparently, neither FocA nor PfFNT exhibited closure or gating.…”

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confidence: 51%

“…On the cellular level, FNTs regulate the metabolic substrate flow and fulfill vital functions, for instance the Plasmodium falciparum PfFNT that we and others identified as the malaria parasite's long-sought lactic acid transporter. 3,4 Blockade of PfFNT by small druglike molecules kills the parasites rendering PfFNT a novel antimalarial drug target. 5,6 Their physiologic relevance as well as structural peculiarities merit a deeper look into the inner workings of the FNTs.…”

mentioning

confidence: 99%

“…2,3 The strictly microbial protein family was named formate-nitrite transporters (FNT) according to the physiologic substrates of the 2 initially characterized members. However, subsequently, the substrate spectrum was extended and comprises several weak monoacids up to the size of lactic acid.…”

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Formate-nitrite transporters: Monoacids ride the dielectric slide

Wiechert

Beitz

2017

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The discovery that the Escherichia coli focA gene product facilitates the transmembrane exchange of formate 1 sparked research on proteins that turned out to be functionally situated between classical transporters and channels. 2,3 The strictly microbial protein family was named formate-nitrite transporters (FNT) according to the physiologic substrates of the 2 initially characterized members. However, subsequently, the substrate spectrum was extended and comprises several weak monoacids up to the size of lactic acid. On the cellular level, FNTs regulate the metabolic substrate flow and fulfill vital functions, for instance the Plasmodium falciparum PfFNT that we and others identified as the malaria parasite's long-sought lactic acid transporter.3,4 Blockade of PfFNT by small druglike molecules kills the parasites rendering PfFNT a novel antimalarial drug target. 5,6 Their physiologic relevance as well as structural peculiarities merit a deeper look into the inner workings of the FNTs.High resolution crystal data revealed a common homopentameric structure.2 The protomers consist of 6 transmembrane spans with both termini at the cytoplasmic side. Surprisingly, FNTs almost perfectly mimic the fold of the aquaporin water and solute channels despite unrelated amino acid sequences. The substrate path through each FNT protomer harbors 2 hydrophobic constrictions, which sandwich the imidazole sidechain of a highly-conserved histidine. The transport mechanism, however, remained unclear regarding to the question whether the substrate anion, e.g. formate, is required to be neutralized by protonation to pass the lipophilic constriction sites.Initially, electrophysiology was used to determine substrate selectivity and pH dependent transport of FocA.2 These studies showed electrogenic, i.e. anion, transport at neutral pH and very low, i.e., channellike, substrate affinity in the high millimolar range. Further, a sudden loss of anion transport was observed when the buffer pH was slightly shifted toward acidic conditions suggesting a gating mechanism for which different conformations of the N-terminal domain were made responsible.2 Together, FocA seemed to behave as a pH-gated anion channel.Due to their weak acidity, e.g., pK a/formate 3.8 and pK a/acetate 4.8, the FNT substrates interconvert between the negatively charged anion and the protonated, neutral acid in a chemical equilibrium. To detect not only the electrogenic anion transport of FocA and PfFNT but additionally capture the transport of the neutral acid substrate species, we used radiolabeled substrates in our assays.3,7 Strikingly and contrary to the electrophysiology studies, we observed increasing transport rates with increasing acidity of the assay media. Apparently, neither FocA nor PfFNT exhibited closure or gating. Further, the alkalization of the media during transport indicated that protons are co-transported with the substrate and disruption of the transmembrane proton gradient revealed that transport is driven by a proton-motive force.7 Together, our da...

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Formate-nitrite transporters: Monoacids ride the dielectric slide

Wiechert

Beitz

2017

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“…A new paper by Beitz and colleagues reports the functional expression of PfFNT in yeast 20 . The authors present evidence that PfFNT transports lactate, formate and a number of other monocarboxylates via a coupled lactate:H þ symport mechanism, and is localized to the parasite surface.…”

Section: Discussionmentioning

confidence: 99%

A lactate and formate transporter in the intraerythrocytic malaria parasite, Plasmodium falciparum

et al. 2015

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The intraerythrocytic malaria parasite relies primarily on glycolysis to fuel its rapid growth and reproduction. The major byproduct of this metabolism, lactic acid, is extruded into the external medium. In this study, we show that the human malaria parasite Plasmodium falciparum expresses at its surface a member of the microbial formate-nitrite transporter family (PfFNT), which, when expressed in Xenopus laevis oocytes, transports both formate and lactate. The transport characteristics of PfFNT in oocytes (pH-dependence, inhibitorsensitivity and kinetics) are similar to those of the transport of lactate and formate across the plasma membrane of mature asexual-stage P. falciparum trophozoites, consistent with PfFNT playing a major role in the efflux of lactate and hence in the energy metabolism of the intraerythrocytic parasite.

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“…The expression system used in this work has been successfully utilized before for the characterization of the Jen homologues of K. lactis (Queirós, et al 2007), C. albicans (Soares-Silva, et al 2004, Vieira, et al 2010), D. hansenii (Soares-Silva et al 2015 and Plasmodium falciparum (Wu, et al 2015). The S. cerevisiae jen1∆ ady2∆ strain (Soares-Silva et al 2011), which presents no activity for the uptake of carboxylates, was used to express the Jen permeases from C. albicans, and K. lactis as well as the ScJen1 mutant alleles.…”

Section: Discussionmentioning

confidence: 99%