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ADPase activity of recombinantly expressed thermotolerant ATPases may be caused by copurification of adenylate kinase of Escherichia coli
Author(s) -
Chen Baoyu,
Sysoeva Tatyana A.,
Chowdhury Saikat,
Guo Liang,
Nixon B. Tracy
Publication year - 2009
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2008.06825.x
Subject(s) - atpase , biochemistry , aquifex aeolicus , pyrococcus furiosus , adenylate kinase , atp hydrolysis , thermophile , escherichia coli , biology , thermoplasma acidophilum , adenosine diphosphate , enzyme , archaea , platelet , platelet aggregation , immunology , gene
Except for apyrases, ATPases generally target only the γ‐phosphate of a nucleotide. Some non‐apyrase ATPases from thermophilic microorganisms are reported to hydrolyze ADP as well as ATP, which has been described as a novel property of the ATPases from extreme thermophiles. Here, we describe an apparent ADP hydrolysis by highly purified preparations of the AAA+ ATPase NtrC1 from an extremely thermophilic bacterium, Aquifex aeolicus . This activity is actually a combination of the activities of the ATPase and contaminating adenylate kinase (AK) from Escherichia coli , which is present at 1/10 000 of the level of the ATPase. AK catalyzes conversion of two molecules of ADP into AMP and ATP, the latter being a substrate for the ATPase. We raise concern that the observed thermotolerance of E. coli AK and its copurification with thermostable proteins by commonly used methods may confound studies of enzymes that specifically catalyze hydrolysis of nucleoside diphosphates or triphosphates. For example, contamination with E. coli AK may be responsible for reported ADPase activities of the ATPase chaperonins from Pyrococcus furiosus , Pyrococcus horikoshii , Methanococcus jannaschii and Thermoplasma acidophilum ; the ATP/ADP‐dependent DNA ligases from Aeropyrum pernix K1 and Staphylothermus marinus ; or the reported ATP‐dependent activities of ADP‐dependent phosphofructokinase of P. furiosus . Purification methods developed to separate NtrC1 ATPase from AK also revealed two distinct forms of the ATPase. One is tightly bound to ADP or GDP and able to bind to Q but not S ion exchange matrixes. The other is nucleotide‐free and binds to both Q and S ion exchange matrixes.