CTEA (
Transporters of the Nramp (Natural resistance-associated macrophage protein) family import divalent transition metal ions into cells of most organisms. By supporting metal homeostasis, Nramps prevent diseases and disorders related to metal insufficiency or overload. Previous studies revealed that Nramps take on a LeuT fold and identified the metal-binding site. We present high-resolution structures of
- Award ID(s):
- 1942763
- NSF-PAR ID:
- 10493349
- Publisher / Repository:
- eLife
- Date Published:
- Journal Name:
- eLife
- Volume:
- 12
- ISSN:
- 2050-084X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract N,N ‐bis[2‐(carboxylmethyl)thioethyl]amine) is a mixed donor ligand that has been incorporated into multiple fluorescent sensors such as NiSensor‐1 that was reported to be selective for Ni2+. Other metal ions such as Zn2+do not produce an emission response in aqueous solution. To investigate the coordination chemistry and selectivity of this receptor, we prepared NiCast, a photocage containing the CTEA receptor. Cast photocages undergo a photoreaction that decreases electron density on a metal‐bound aniline nitrogen atom, which shifts the binding equilibrium toward unbound metal ion. The unique selectivity of CTEA was examined by measuring the binding affinity of NiCast and the CTEA receptor for Ni2+, Zn2+, Cd2+and Cu2+under different conditions. In aqueous solution, Ni2+binds more strongly to the aniline nitrogen atom than Cd2+; however, in CH3CN, the change in affinity virtually disappears. The crystal structure of [Cu(CTEA)], which exhibits a Jahn–Teller–distorted square pyramidal structure, was also analyzed to gain more insight into the underlying coordination chemistry. These studies suggest that the fluorescence selectivity of NiSensor‐1 in aqueous solution is due to a stronger interaction between the aniline nitrogen atom and Ni2+compared to other divalent metal ions except Cu2+. -
Abstract Background and aims Rice is prone to Cd uptake under aerobic soil conditions primarily due to the OsNramp5 Mn transport pathway. Unlike Cd, Mn availability in rice paddies decreases as redox potential increases. We tested whether increasing Mn concentrations in solution would decrease Cd accumulation in rice through competition between Mn and Cd for uptake and/or suppression of
OsNramp5 expression.Methods Rice was grown to maturity under Mn concentrations that spanned three orders of magnitude (0.30 to 37 μM) that corresponded to free Mn2+activities of 10–7.9to 10–5.0 M while free Cd2+activity was held as constant as achievable (10–10.2to 10–10.4 M). Plant biomass and elemental concentrations were measured in roots and shoots at each stage. Fold changes in the expression of
OsNramp5 ,OsCd1 ,OsHMA3 ,OsCCX2 , andOsYSL6 genes in vegetative and grain-filling stages of rice plants were determined.Results Competition between Mn and Cd for root uptake and accumulation in shoots was observed at the highest concentration of Mn tested.
OsNramp5 expression was significantly higher in rice plants at the vegetative stage compared to the grain-filling stage, whileOsCd1 andOsHMA3 showed the opposite. Solution Mn concentrations previously thought to be tolerable by rice grown to the vegetative stage led to Mn toxicity as plants matured.Conclusions Mn competes with Cd during uptake into rice with
OsNramp5 expression unaffected. Different translocation paths may occur for Mn and Cd within the rice plant and over the rice life cycle, withOsCCX2 correlated with shoot Cd concentration. -
Long-range dynamic correlations regulate the catalytic activity of the bacterial tyrosine kinase Wzcnull (Ed.)BY-kinases represent a highly conserved family of protein tyrosine kinases unique to bacteria without eukaryotic orthologs. BY-kinases are regulated by oligomerization-enabled transphosphorylation on a C-terminal tyrosine cluster through a process with sparse mechanistic detail. Using the catalytic domain (CD) of the archetypal BY-kinase, Escherichia coli Wzc, and enhanced-sampling molecular dynamics simulations, isothermal titration calorimetry and nuclear magnetic resonance measurements, we propose a mechanism for its activation and nucleotide exchange. We find that the monomeric Wzc CD preferentially populates states characterized by distortions at its oligomerization interfaces and by catalytic element conformations that allow high-affinity interactions with ADP but not with ATP·Mg 2+ . We propose that oligomer formation stabilizes the intermonomer interfaces and results in catalytic element conformations suitable for optimally engaging ATP·Mg 2+ , facilitating exchange with bound ADP. This sequence of events, oligomerization, i.e., substrate binding, before engaging ATP·Mg 2+ , facilitates optimal autophosphorylation by preventing a futile cycle of ATP hydrolysis.more » « less
-
Summary Marine bacterioplankton face stiff competition for limited nutrient resources. SAR11, a ubiquitous clade of very small and highly abundant
Alphaproteobacteria , are known to devote much of their energy to synthesizing ATP‐binding cassette periplasmic proteins that bind substrates. We hypothesized that their small size and relatively large periplasmic space might enable them to outcompete other bacterioplankton for nutrients. Using uptake experiments with14C‐glycine betaine, we discovered that two strains of SAR11,Candidatus Pelagibacter sp. HTCC7211 andCand . P. ubique HTCC1062, have extraordinarily high affinity for glycine betaine (GBT), with half‐saturation (K s ) values around 1 nM and specific affinity values between 8 and 14 L mg cell−1 h−1. Competitive inhibition studies indicated that the GBT transporters in these strains are multifunctional, transporting multiple substrates in addition to GBT. Both strains could use most of the transported compounds for metabolism and ATP production. Our findings indicate thatPelagibacter cells are primarily responsible for the high affinity and multifunctional GBT uptake systems observed in seawater. Maximization of whole‐cell affinities may enable these organisms to compete effectively for nutrients during periods when the gross transport capacity of the heterotrophic plankton community exceeds the supply, depressing ambient concentrations. -
Abstract Methionine (Met) cationized with Zn2+, forming Zn (Met–H)+(ACN) where ACN = acetonitrile, Zn (Met–H)+, and ZnCl+(Met), as well as Cd2+, forming CdCl+(Met), were examined by infrared multiple photon dissociation (IRMPD) action spectroscopy using light generated from the FELIX free electron laser. A series of low‐energy conformers for each complex was found using quantum‐chemical calculations in order to identify the structures formed experimentally. For all four complexes, spectral comparison indicated that the main binding motif observed is a charge solvated, tridentate structure where the metal center binds to the backbone amino group nitrogen, backbone carbonyl oxygen (where the carboxylic acid is deprotonated in two of the Zn2+complexes), and side‐chain sulfur. For all species, the predicted ground structures reproduce the experimental spectra well, although low‐lying conformers characterized by similar binding motifs may also contribute in each system. The current work provides valuable information regarding the binding interaction between Met and biologically relevant metals. Further, the comparison between the current work and previous analyses involving alkali metal cationized Met as well as cysteine (the other sulfur containing amino acid) cationized with Zn2+and Cd2+allows for the elucidation of important metal dependent trends associated with physiologically important metal–sulfur binding.