Characterization of Amino Acid Substitutions in KdpA, the K + -Binding and -Translocating Subunit of the KdpFABC Complex of Escherichia coli

Abstract
When grown under K + limitation, Escherichia coli induces the K + -translocating KdpFABC complex. The stimulation of ATPase activity by NH 4 + ions was shown for the first time. Substitutions in KdpA, which is responsible for K + binding and translocation, revealed that enzyme complexes KdpA:G232A and KdpA:G232S have completely lost their cation selectivity.