TY - JOUR ID - 10442/8338 A1 - Theodorou, M. C. A1 - A1 - Tiligada, E. A1 - A1 - Kyriakidis, D. A. Y1 - 2009/// T1 - Extracellular Ca2+ transients affect poly-(R)-3-hydroxybutyrate regulation by the AtoS-AtoC system in Escherichia coli JF - Biochemical Journal VL - 417 SN - 0264-6021 U3 - 10.1042/bj20081169 PB - Portland Press, Great Britain SP - 667–672EP - UR - https://hdl.handle.net/10442/8338 N2 - Escherichia coli is exposed to wide extracellular concentrations of Ca2+, whereas the cytosolic levels of the ion are subject to stringent control and are implicated in many physiological functions. The present study shows that extracellularCa2+ controls cPHB [complexed poly-(R)-3-hydroxybutyrate] biosynthesis through the AtoS-AtoC two-component system. Maximal cPHB accumulation was observed at higher [Ca2+]e (extracellular Ca2+ concentration) in AtoS-AtoC-expressing E. coli compared with their _atoSC counterparts, in both cytosolic and membrane fractions. The reversal of EGTA-mediated down-regulation of cPHB biosynthesis by the addition of Ca2+ and Mg2+ was under the control of the AtoS-AtoC system.Moreover, the Ca2+-channel blocker verapamil reduced total and membrane-bound cPHB levels, the inhibitory effect being circumvented by Ca2+ addition only in atoSC+ bacteria. Histamine and compound 48/80 affected cPHB accumulation in a [Ca2+]e-dependent manner directed by theAtoS-AtoC system. In conclusion, these data provide evidence for the involvement of external Ca2+ on cPHB synthesis regulated by the AtoS-AtoC two-component system, thus linking Ca2+ with a signal transduction system, most probably through a transporter. Key words: AtoS-AtoC two-component system, atoDAEB, calcium, calcium channel blocker, histamine, poly-(R)-3- hydroxybutyrate. ER -