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J Mol Biol. 2019 May 31;431(12):2331-2342. doi: 10.1016/j.jmb.2019.04.040. Epub 2019 May 6.

Potential Regulatory Role of Competitive Encounter Complexes in Paralogous Phosphotransferase Systems.

Author information

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. Electronic address: peterkoa@nhlbi.nih.gov.
4
Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA. Electronic address: tjandran@nhlbi.nih.gov.

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.

KEYWORDS:

Enzyme I; NMR; encounter complex; nitrogen phosphotransferase system (PTS(Ntr)); paramagnetic relaxation enhancement (PRE)

PMID:
31071328
PMCID:
PMC6554058
[Available on 2020-05-31]
DOI:
10.1016/j.jmb.2019.04.040

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