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Applied Biochemistry and Biotechnology

, Volume 117, Issue 1, pp 33–48 | Cite as

Characterization and comparison of metal accumulation in two Escherichia coli strains expressing either CopA or MntA, heavy metal-transporting bacterial P-type adenosine triphosphatases

  • Nick Zagorski
  • David B. WilsonEmail author
Original Articles

Abstract

MntA from Lactobacillus plantarum and copA from Enterococcus hirae both encode membrane proteins that are members of the P-type family of adenosine triphosphatases (ATPases). Both transporters act as metal importers to take up nutritionally required substrates; MntA translocates Mn(II) and CopA translocates Cu(I). Both ATPases can also translocate secondary substrates, Cd(II) and Ag(I), respectively. Although functionally and sequentially similar, these ATPases differ in several key residues and in their membrane topologies. The bioaccumulation properties of these two proteins were examined by coexpressing the transporters with overexpressed metallothionein in Escherichia coli cells, a system that has previously shown high levels of substrate-specific uptake. Both strains exhibited rapid metal accumulation, both saturated at around 50 µM metal, and both displayed temperature-sensitive uptake. However, the transporters responded differently when external conditions were varied; MntA displayed increased sensitivity to ionic strength, while CopA was more pH sensitive and more inhibited by chelating agents. The differences in accumulation are likely owing to structural differences in the transmembrane region of these two ATPases.

Index Entries

Ion transport P-type adenosine triphosphatase copper cadmium genetic engineering metallothionein lactobacillus enterococcus Escherichia coli 

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Copyright information

© Humana Press Inc. 2004

Authors and Affiliations

  1. 1.Department of Molecular Biology and GeneticsCornell UniversityIthaca

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