Epstein W
Department of Molecular Genetics and Cell Biology, University of Chicago.
Acta Physiol Scand Suppl. 1992;607:193-9.
The Kdp ATPase is a P-type ATPase consisting of three large protein subunits in a complex that probably contains 2 copies of each subunit. A small hydrophobic peptide, encoded in the same operon as the large subunits, may also participate. Kdp has very high affinity for K+ and serves to scavenge this ion when its concentration is low. Kdp responds to turgor pressure at two levels, at the level of activity and of expression. Kdp mediates net uptake when turgor is low, but mediates exchange without net change when turgor is normal. Kdp is expressed only when turgor is low. This control is mediated by a pair of regulatory proteins, members of the class of 'sensor-effector' regulators widely distributed in bacteria. It is suggested that low turgor changes the conformation of the KdpD 'sensor' protein, activating its presumed kinase activity to phosphorylate KdpE, the 'effector' protein, and phospho-KdpE in turn turns on expression of the operon that encodes the Kdp complex.
Kdp ATP酶是一种P型ATP酶，由三个大的蛋白质亚基组成一个复合体，每个亚基可能有两个拷贝。与大亚基在同一操纵子中编码的一个小的疏水肽也可能参与其中。Kdp对K+具有很高的亲和力，当K+浓度较低时，它用于清除这种离子。Kdp在活性和表达两个水平上对膨压作出反应。当膨压较低时，Kdp介导净摄取，但当膨压正常时，它介导交换而无净变化。Kdp仅在膨压较低时表达。这种调控由一对调节蛋白介导，它们是广泛分布于细菌中的“传感器-效应器”调节蛋白家族的成员。有人提出，低膨压会改变KdpD“传感器”蛋白的构象，激活其假定的激酶活性，使其磷酸化“效应器”蛋白KdpE，而磷酸化的KdpE反过来会开启编码Kdp复合体的操纵子的表达。
