The high-affinity K+-translocating ATPase complex from Clostridium acetobutylicum consists of six subunits

The kdp operon of Clostridium acetobutylicum codes for the high affinity K-translocating Kdp system (P-type ATPase). Beside the three large proteins KdpA, KdpB and KdpC, the kdp operon encodes the two small peptides KdpZ, Kd pY and the KdpX protein. The truncation of the clostridial kdpZ and/or the kdpY gene has a significant impact on the growth of an E. coli mutant (TK22 05), which is unable to grow at low potassium concentrations. These two gen es together with kdpX are essential to maintain the wild-type K+-pump capac ity of the clostridial Kdp system. Also the ATPase activity itself, the sub strate specifity, and the cation specifity are determined in a major way by KdpZ, KdpY, and KdpX. Thus, this report shows the importance of the KdpZ, KdpY, and KdpX proteins for the Kdp-ATPase and therefore the corresponding operon should now be referred to as kdpZYABCX. (C) 2001 Academic Press.