Asp804 and Asp808 in the Transmembrane Domain of the Na,K-ATPase α Subunit Are Cation Coordinating Residues

Abolishment of Proton Pumping and Accumulation in the E1P Conformational State of a Plant Plasma Membrane H+-ATPase by Substitution of a Conserved Aspartyl Residue in Transmembrane Segment 6

“…It has previously been suggested that M5 and M6 move in and out of the membrane during catalysis in a cation-dependent manner (16). Our results support the notion that Asp 684 in M6 could be required for this movement of the transmembrane helices (12). This article cites 39 references, 18 of which can be accessed free at…”

“…Therefore, it appears that the inability to support yeast growth is due to a specific effect of Asp 684 on the function of the machinery involved in the catalytic cycle of the plasma membrane H ϩ -ATPase. In line with this observation, Asp 808 substitutions in Na ϩ / K ϩ -ATPase bind ATP with similar affinities as the wild-type enzyme (12)(13) 684 substitution is the dephosphorylation step. Several lines of evidence suggested to us that it was the E 1 P form of the mutant enzyme that accumulated: (i) the phosphoenzyme was sensitive to ADP, which interacts specifically with the E 1 P form of P-type ATPases; (ii) during trypsinolysis, both aha2⌬73 and the Asp 684 substitution were protected by ATP, which binds to E 1 , whereas vanadate, an inhibitor which binds to the E 2 conformation, protected only a fragment of aha2⌬73; (iii) ATP hydrolysis by the mutant was completely insensitive toward vanadate.…”

“…For example, most of the extramembraneous regions of the Na ϩ /K ϩ -ATPase can be removed by proteolytic digestion while the remaining portion of the enzyme maintains its ability to bind and occlude K ϩ (10). Furthermore, mutagenesis studies have identified a number of amino acid residues within M4, M5, and M6 of the Na ϩ /K ϩ -ATPase that appear to be critical for cation binding (11)(12)(13)(14). These residues are in general polar, and most are negatively charged.…”

Characterization of a Thermophilic P-type Ag+/Cu+-ATPase from the ExtremophileArchaeoglobus fulgidus

“…The phosphorylation of the aspartyl group in the consensus sequence DKTGT is a fundamental characteristic within this mechanism. The participation of specific transmembrane segments (TMs) in cation binding and transport has also been established for the better characterized members of this family, the Na,K-ATPase and SR Ca-ATPase (5)(6)(7)(8). Recently, the structure of the SR Ca-ATPase (2.6-Å resolution) was reported (9).…”

Functional Consequences of Alterations to Ile279, Ile283, Glu284, His285, Phe286, and His288 in the NH2-terminal Part of Transmembrane Helix M3 of the Na+,K+-ATPase

“…1, red residues; Refs. [7][8][9][10][11][12][13][14][15][16]. Several of these residues are conserved in the Ca 2ϩ -ATPase and donate ligands to Ca 2ϩ binding (17)(18)(19)(20).…”