Transmembrane modulator-dependent bacterial tyrosine kinase activates UDP-glucose dehydrogenases.

I. Mijakovic (1) , S. Poncet (1) , G. Boel (1) , A. Maze (1) , S. Gillet (1) , E. Jamet (1) , P. Decottignies (1) , C. Grangeasse (1) , P. Doublet (1) , P. Lemarechal (1) , J. Deutscher (1)

1 IBCP - Institut de biologie et chimie des protéines [Lyon]

Protein-tyrosine kinases regulating bacterial exopolysaccharide synthesis autophosphorylate on tyrosines located in a conserved C-terminal region. So far no other substrates have been identified for these kinases. Here we demonstrate that Bacillus subtilis YwqD not only autophosphorylates at Tyr-228, but that it also phosphorylates the two UDP-glucose dehydrogenases (UDP-glucose DHs) YwqF and TuaD at a tyrosine residue. However, phosphorylation of YwqF and TuaD occurs only in the presence of the transmembrane protein YwqC. The presumed intracellular C-terminal part of YwqC (last 50 amino acids) seems to interact with the tyrosine-kinase and to allow YwqD-catalysed phosphorylation of the two UDP-glucose DHs, which are key enzymes for the synthesis of acidic polysaccharides. However, only when phosphorylated by YwqD do the two enzymes exhibit detectable UDP-glucose DH activity. Dephosphorylation of P-Tyr-YwqF and P-Tyr-TuaD by the P-Tyr-protein phosphatase YwqE switched off their UDP-glucose DH activity. YwqE, which is encoded by the fourth gene of the B.subtilis ywqCDEF operon, also dephosphorylates P-Tyr-YwqD.Protein-tyrosine kinases regulating bacterial exopolysaccharide synthesis autophosphorylate on tyrosines located in a conserved C-terminal region. So far no other substrates have been identified for these kinases. Here we demonstrate that Bacillus subtilis YwqD not only autophosphorylates at Tyr-228, but that it also phosphorylates the two UDP-glucose dehydrogenases (UDP-glucose DHs) YwqF and TuaD at a tyrosine residue. However, phosphorylation of YwqF and TuaD occurs only in the presence of the transmembrane protein YwqC. The presumed intracellular C-terminal part of YwqC (last 50 amino acids) seems to interact with the tyrosine-kinase and to allow YwqD-catalysed phosphorylation of the two UDP-glucose DHs, which are key enzymes for the synthesis of acidic polysaccharides. However, only when phosphorylated by YwqD do the two enzymes exhibit detectable UDP-glucose DH activity. Dephosphorylation of P-Tyr-YwqF and P-Tyr-TuaD by the P-Tyr-protein phosphatase YwqE switched off their UDP-glucose DH activity. YwqE, which is encoded by the fourth gene of the B.subtilis ywqCDEF operon, also dephosphorylates P-Tyr-YwqD.

Mots clés: P‐Tyrosine Phosphatase; Polysaccharide Synthesis; Protein Phosphorylation; Tyrosine‐Kinase; UDP‐Glucose Dehydrogenase

Domaines: Biochimie, Biologie Moléculaire

I. Mijakovic, S. Poncet, G. Boel, A. Maze, S. Gillet, et al.. Transmembrane modulator-dependent bacterial tyrosine kinase activates UDP-glucose dehydrogenases.. EMBO Journal, 2003, 22 (18), pp.4709-4718. ⟨10.1093/emboj/cdg458⟩. ⟨hal-00314354⟩