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Elucidation of M g 2+ binding activity of adenylate kinase from M ycobacterium tuberculosis H 37 R v using fluorescence studies
Author(s) -
Meena Laxman S.,
Dhakate Sanjay R.,
Sahare Purushottam D.
Publication year - 2012
Publication title -
biotechnology and applied biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.468
H-Index - 70
eISSN - 1470-8744
pISSN - 0885-4513
DOI - 10.1002/bab.1043
Subject(s) - adenylate kinase , biochemistry , enzyme , adenosine triphosphate , chemistry , nucleotide , adenosine monophosphate , adenosine diphosphate , cyclase , nucleoside diphosphate kinase , nucleoside triphosphate , microbiology and biotechnology , biology , platelet , platelet aggregation , immunology , gene
Adenylate kinase ( AK ) is a small ubiquitous enzyme that catalyzes the reversible transfer of the terminal phosphate group from adenine triphosphate ( ATP ): magnesium ion ( M g 2+ ) to adenine monophosphate ( AMP ) to form two molecules of adenine diphosphate ( ADP ). AK thus maintains the homeostasis of adenine nucleotides in eukaryotes and prokaryotes. Because the [ ATP ]/[ ADP ] ratio is an important parameter in energy regulation in cells, M g 2+ ‐activated AK has an important biological role, particularly in the case of bacteria, as imbalance in the ratio of [ ATP ]/[ ADP ] has been associated with alteration in its DNA supercoiling state. In the present study, magnesium‐binding assays were carried out by systematically varying the concentrations of M g 2+ , protein, AMP , ATP , and indicator in kinetic experiments. We report evidence that during magnesium‐binding assay, the fluorescence level of the indicator “ M ag‐ I ndo‐1” changes with protein concentration, suggesting that magnesium ions are binding to AK . The dual activity of AK both as nucleoside monophosphate and diphosphate kinases suggests that this enzyme may have a role in RNA and DNA biosynthesis in addition to its role in intracellular nucleotide metabolism. According to the proposed model, the magnesium‐activated AK exhibits an increase in its forward reaction rate compared with the inactivated form. These findings imply that M g 2+ could be an important regulator in the energy signaling network in cells.