Extracellular Ca2+ transients affect poly-(R)-3-hydroxybutyrate regulation by the AtoS-AtoC system in Escherichia coli

• Published in: Biochemical journal Vol. 417; no. 3; p. 667
• Main Authors: Theodorou, Marina C, Tiligada, Ekaterini, Kyriakidis, Dimitrios A
• Format: Journal Article
• Language: English
• Published: England 01.02.2009
• Subjects: Calcium - metabolism; DNA-Binding Proteins - metabolism; Escherichia coli - genetics; Escherichia coli - metabolism; Escherichia coli Proteins - metabolism; Hydroxybutyrates - metabolism; Polyesters - metabolism; Protein Kinases - metabolism; Signal Transduction
• ISSN: 1470-8728
• DOI: 10.1042/BJ20081169

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 extracellular Ca2+ 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 DeltaatoSC 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 the AtoS-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.