A possible regulatory role for the metal-binding domain of CadA, the Listeria monocytogenes Cd2+-ATPase

Using the baculovirus/Sf9 expression system, we produced CadA and Delta MBD , a metal-binding domain, truncated CadA. Both proteins had the expected pr operties of P-type ATPases: ATP-induced Cd2+ accumulation, Cd2+-sensitive A TP and Pi phosphorylation and ATPase activity. Delta MBD displayed lower in itial transport velocity as well as lower maximal ATPase activity than CadA . MBD truncation flattened the Cd2+ dependence of the ATPase activity and i ncreased apparent Cd2+ affinity, suggesting a positive cooperativity betwee n MBD and membranous transport sites. We propose that occupancy of MBD by C d2+ modulates CadA activity. (C) 2001 Federation of European Biochemical So cieties. Published by Elsevier Science B.V. All rights reserved.