Post-translational modifications (PTMs) add regulatory features to proteins that help establish the complex functional networks that make up higher organisms. Advances in analytical detection methods have led to the identification of more than 200 types of PTMs. However, some modifications are unstable under the present detection methods, anticipating the existence of further modifications and a much more complex map of PTMs. An example is the recently discovered protein modification polyphosphorylation. Polyphosphorylation is mediated by inorganic polyphosphate (polyP) and represents the covalent attachment of this linear polymer of orthophosphate to lysine residues in target proteins. This modification has eluded MS analysis as both polyP itself and the phosphoramidate bonds created upon its reaction with lysine residues are highly unstable in acidic conditions. Polyphosphorylation detection was only possible through extensive biochemical characterization. Two targets have been identified: nuclear signal recognition 1 (Nsr1) and its interacting partner, topoisomerase 1 (Top1). Polyphosphorylation occurs within a conserved N-terminal polyacidic serine (S) and lysine (K) rich (PASK) cluster. It negatively regulates Nsr1–Top1 interaction and impairs Top1 enzymatic activity, namely relaxing supercoiled DNA. Modulation of cellular levels of polyP regulates Top1 activity by modifying its polyphosphorylation status. Here we discuss the significance of the recently identified new role of inorganic polyP.
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February 2016
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Scanning electron micrograph of a cell from the endosperm of a barley grain. The cell is tightly packed with large, disk-shaped (A-type) and much smaller, almost spherical (B-type) starch granules. The smooth areas in this image are the surface of the cell walls of neighbouring endosperm cells. For further details see pp. 157-163. Image kindly provided by Elaine Barclay and Vasilios Andriotis (John Innes Centre, Norwich). - PDF Icon PDF LinkTable of Contents
Review Article|
February 09 2016
The new world of inorganic polyphosphates
Cristina Azevedo;
Cristina Azevedo
1
*Medical Research Council Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, U.K.
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Adolfo Saiardi
Adolfo Saiardi
1
*Medical Research Council Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, U.K.
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Publisher: Portland Press Ltd
Received:
November 20 2015
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© 2016 Authors; published by Portland Press Limited
2016
Biochem Soc Trans (2016) 44 (1): 13–17.
Article history
Received:
November 20 2015
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A correction has been published:
Correction: The new world of inorganic polyphosphates
Citation
Cristina Azevedo, Adolfo Saiardi; The new world of inorganic polyphosphates. Biochem Soc Trans 15 February 2016; 44 (1): 13–17. doi: https://doi.org/10.1042/BST20150210
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