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 DeltaMBD, a metal-binding domain, truncated CadA. Both proteins had the expected properties of P-type ATPases: ATP-induced Cd2+ accumulation, Cd2+-sensitive ATP and Pi phosphorylation and ATPase activity. DeltaMBD displayed lower initial transport velocity as well as lower maximal ATPase activity than CadA. MBD truncation flattened the Cd2+ dependence of the ATPase activity and increased apparent Cd2+ affinity, suggesting a positive cooperativity between MBD and membranous transport sites. We propose that occupancy of MBD by Cd2+ modulates CadA activity.