Mutagenesis of glutamate 820 of the gastric H+,K+-ATPase alpha-subunit to aspartate decreases the apparent ATP affinity.
Mutagenesis of Glu820, present in the catalytic subunit of gastric H+,K+-ATPase, into an Asp hardly affects K+-stimulated ATPase and K+-stimulated dephosphorylation of the enzyme. The ATP phosphorylation rate of the E820D mutant, however, is rather low and the apparent affinity for ATP in the phosphorylation process of this mutant is 2-3 times lower than that of the wild type enzyme. The reduction in the ATP phosphorylation rate of the E820D mutant has only an effect on the ATPase activity at low temperature. These findings suggest that Glu820 might play a role in H+ stimulation of the phosphorylation process.
Hermsen
H P
HP
Department of Biochemistry, Institute of Cellular Signalling, University of Nijmegen, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands.
Swarts
H G
HG
Koenderink
J B
JB
De Pont
J J
JJ
D000255:Adenosine Triphosphate / Q000378:metabolism*; D001224:Aspartic Acid / Q000737:chemistry*; D018698:Glutamic Acid / Q000737:chemistry*; D017506:H(+)-K(+)-Exchanging ATPase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010766:Phosphorylation; D013696:Temperature
D001224:Aspartic Acid; D018698:Glutamic Acid; D000255:Adenosine Triphosphate; D017506:H(+)-K(+)-Exchanging ATPase