Potential Regulatory Role of Competitive Encounter Complexes in Paralogous Phosphotransferase Systems |
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| Institution: | 1. Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA;2. Office of Intramural Research, Center for Information Technology, National Institutes of Health, Bethesda, MD 20892, USA;3. Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA;1. Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA;2. Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA;3. Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA;4. Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, New York, NY, USA;5. School of Health Sciences, Purdue University, 915 W State St., LILYG-227, West Lafayette, IN 47907, USA;6. Purdue Institute for Integrative Neuroscience, 915 W State St., LILYG-227, West Lafayette, IN 47907, USA;7. Purdue Institute for Inflammation, Immunology and Infectious Disease, Purdue University, 915 W State St., LILYG-227, West Lafayette, IN 47907, USA;1. Ludwig-Maximilians-Universitaet Muenchen, Mikrobiologie, Großhaderner Str. 2-4, 82152, Martinsried, Germany;2. Technical University of Munich, Physics of Complex Biosystems, James-Franck-Str. 1, 85748 Garching, Germany;3. University of Göttingen, Institute for Microbiology and Genetics, Dept. of General Microbiology, Grisebachstr. 8, 37077 Göttingen, Germany;1. Center for Integrated Protein Science at the Department of Chemistry and Institute for Advanced Study, Technical University of Munich, 85748 Garching, Germany;2. Center for Integrated Protein Science at the Physics Department, Technical University of Munich, 85748 Garching, Germany |
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| Abstract: | There are two paralogous Escherichia coli phosphotransferase systems, one for sugar import (PTSsugar) and one for nitrogen regulation (PTSNtr), that utilize proteins enzyme Isugar (EIsugar) and HPr, and enzyme INtr (EINtr) and NPr, respectively. The enzyme I proteins have similar folds, as do their substrates HPr and NPr, yet they show strict specificity for their cognate partner both in stereospecific protein–protein complex formation and in reversible phosphotransfer. Here, we investigate the mechanism of specific EINtr:NPr complex formation by the study of transient encounter complexes. NMR paramagnetic relaxation enhancement experiments demonstrated transient encounter complexes of EINtr not only with the expected partner, NPr, but also with the unexpected partner, HPr. HPr occupies transient sites on EINtr but is unable to complete stereospecific complex formation. By occupying the non-productive transient sites, HPr promotes NPr transient interaction to productive sites closer to the stereospecific binding site and actually enhances specific complex formation between NPr and EINtr. The cellular level of HPr is approximately 150 times higher than that of NPr. Thus, our finding suggests a potential mechanism for cross-regulation of enzyme activity through formation of competitive encounter complexes. |
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