Evidence that bacterial ABC-type transporter imports free EDTA for metabolism

Hua Zhang; Jacob P Herman; Harvey Bolton, Jr; Zhicheng Zhang; Sue Clark; Luying Xun

doi:10.1128/JB.01164-07

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Evidence that bacterial ABC-type transporter imports free EDTA for metabolism

Journal article

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Peer reviewed

Evidence that bacterial ABC-type transporter imports free EDTA for metabolism

Hua Zhang, Jacob P Herman, Harvey Bolton, Jr, Zhicheng Zhang, Sue Clark and Luying Xun

Journal of bacteriology, Vol.189(22), pp.7991-7997

11/2007

DOI: https://doi.org/10.1128/JB.01164-07

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https://hdl.handle.net/2376/103071

PMCID: PMC2168656

PMID: 17873047

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Abstract

Water Pollutants, Chemical - metabolism

Metals - metabolism

Edetic Acid - chemistry

Metals - chemistry

Time Factors

Rhizobiaceae - metabolism

ATP-Binding Cassette Transporters - metabolism

Edetic Acid - metabolism

Periplasmic Binding Proteins - genetics

Periplasmic Binding Proteins - metabolism

EDTA, a common chelating agent, is becoming a major organic pollutant in the form of metal-EDTA complexes in surface waters, partly due to its recalcitrance to biodegradation. Even an EDTA-degrading bacterium, BNC1, does not degrade stable metal-EDTA complexes. In the present study, an ABC-type transporter was identified for possible uptake of EDTA because the transporter genes and the EDTA monooxygenase gene were expressed from a single operon in BNC1. The ABC-type transporter had a periplasmic-binding protein (EppA) that should confer the substrate specificity for the transporter; therefore, EppA was produced in Escherichia coli, purified, and characterized. EppA was shown to bind free EDTA with a dissociation constant as low as 25 nM by using isothermal titration calorimetry. When unstable metal-EDTA complexes, e.g., (Mg-EDTA)(2-), were added to the EppA solution, binding was also observed. However, experimental data and theoretical analysis supported EppA binding only of free EDTA. When stable metal-EDTA complexes, e.g., (Cu-EDTA)(2-), were titrated into the EppA solution, no binding was observed. Since EDTA monooxygenase in the cytoplasm uses some of the stable metal-EDTA complexes as substrates, we suggest that the lack of EppA binding and EDTA uptake are responsible for the failure of BNC1 cells to degrade the stable complexes.

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Title: Evidence that bacterial ABC-type transporter imports free EDTA for metabolism
Creators: Hua Zhang - School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4234, USA
Jacob P Herman
Harvey Bolton, Jr
Zhicheng Zhang
Sue Clark
Luying Xun
Publication Details: Journal of bacteriology, Vol.189(22), pp.7991-7997
Academic Unit: Chemistry, Department of; Molecular Biosciences, School of
Publisher: United States
Identifiers: 99900546643601842
Language: English
Resource Type: Journal article