Substrate Specificity of the Bacillus subtilis BY-Kinase PtkA Is Controlled by Alternative Activators: TkmA and SalA

Abderahmane Derouiche, Lei Shi, Aida Kalantari, Ivan Mijakovic

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Abstract

Bacterial protein-tyrosine kinases (BY-kinases) are known to regulate different aspects of bacterial physiology, by phosphorylating cellular protein substrates. Physiological cues that trigger BY-kinases activity are largely unexplored. In Proteobacteria, BY-kinases contain a cytosol-exposed catalytic domain and a transmembrane activator domain in a single polypeptide chain. In Firrnicutes, the BY-kinase catalytic domain and the transmembrane activator domain exist as separate polypeptides. We have previously speculated that this architecture might enable the Firmicutes BY-kinases to interact with alternative activators, and thus account for the observed ability of these kinases to phosphorylate several distinct classes of protein substrates. Here, we present experimental evidence that supports this hypothesis. We focus on the model Firmicute-type BY-kinase PtkA from Bacillus subtilis, known to phosphorylate several different protein substrates. We demonstrate that the transcriptional regulator SaIA, hitherto known as a substrate of PtkA, can also act as a PtkA activator. In doing so, SaIA competes with the canonical PtkA activator, TkmA. Our results suggest that the respective interactions of SaIA and TkmA with PtkA favor phosphorylation of different protein substrates in vivo and in vitro. This observation may contribute to explaining how specificity is established in the seemingly promiscuous interactions of BY-kinases with their cellular substrates.
Original languageEnglish
Article number1525
JournalFrontiers in Microbiology
Volume7
Number of pages7
ISSN1664-302X
DOIs
Publication statusPublished - 2016

Bibliographical note

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

Keywords

  • Bacterial protein-tyrosine kinase
  • Protein phosphorylation
  • Kinase specificity
  • Kinase activator
  • Transcription factor

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