%0 Journal Article %A Filippou, P. S.%A %A Kasemian, L. D.%A %A Panagiotidis, C. A.%A %A Kyriakidis, D.A. %D 2007 %T Identification of the phosphorylation site of the histidine kinase of E. coli AtoS-AtoC two-component system %J The FEBS Journal %V 274 %@ 1742-464X %R 10.1111/j.0014-2956.2007.05861_3.x %I Wiley-Blackwell Publishing Ltd. %P 149–149 %N Suppl 1 %U https://hdl.handle.net/10442/7940 %X The sensor histidine kinase AtoS together with AtoC/Az constitute a two-component signal transduction system (TCS) in E. coli, involved in the regulation of the atoDAEB operon. Upon activation by acetoacetate, AtoS autophosphorylates and subsequently phosphorylates AtoC which is essential for the transcriptional regulation of the atoDAEB operon, the products of which are involved in the catabolism of short-chain fatty acids. AtoS, has the structural characteristics of an integral membrane protein and structurally comprises three putative transmembrane domains, a HAMP, a PAS, a PAC and the catalytic domain of the histidine kinase. Sequence comparisons with other histidine kinases revealed the presence of a characteristic ‘“H-box”’ in AtoS with histidine-398 as a possible phosphorylation site. In the present study, chemical stability tests of phosphorylated cytosolic form of AtoS, and substitution of histidine-398 to leucine through site directed mutagenesis, pointed towards the direction that histidine is indeed the phosphorylated residue in AtoS. The alteration of this putative phosphorylation site has also been demonstrated to affect the biological activity of AtoS, i.e. its ability to activate AtoC and induce ato operon expression upon acetoacetate induction %> Αποθετήριο Ήλιος / ΕΙΕ