We compared the pH dependence of the human Cu2+ ATPase ATP7B with the Ca2+ ATPase SERCA. X2+/H+ exchange is a specific feature of SERCA, which is not observed in ATP7B.
Data from Tadini-Buoninsegni et al, 2010
Background and Assay Description:
The authors performed 100 μM ATP concentration jumps on samples containing the Ca2+-ATPase SERCA and the Cu2+-ATPase ATP7B. The measurement solutions contained 10 μM free Ca2+ for the SERCA assay and 5 μM CuCl2 for the ATP7B assay. To conclude the effect of pH on transport activity, measurement solutions with two different pH values are compared on the same sensor for both transporters.
Impact of the data:
In the case of SERCA the current signal decreases as the pH is raised. It is known that Ca2+/H+ exchange is a specific feature of SERCA, facilitating luminal Ca2+ release. Our results indicate that a low H+ concentration (i.e., alkaline pH) interferes with Ca2+/H+ exchange, thereby preventing translocation and release of bound Ca2+. Contrary to SERCA, ATP-dependent charge movement in ATP7B is not altered by varying the pH, thereby suggesting that Cu+/H+ exchange may not be required for lumenal copper release.
Author: Francesco Tadini-Buoninsegni, University of Florence
Target: ATP7B, SERCA
Family / Type: p-type ATPases
Mode of transport: ATP-driven Cu2+ and Ca2+ transport
Sample: COS-1 microsomes (ATP7B), sarcoplasmic reticulum vesicles from the hind leg muscles of New Zealand White Rabbits (SERCA)
Expression: Recombinant (ATP7B), native (SERCA)
Platform: SURFE²R N1