Selective Fe2+-catalyzed oxidative cleavage of gastric H+,K+-ATPase: implications for the energy transduction mechanism of P-type cation pumps.
In the presence of ascorbate/H(2)O(2), Fe(2+) ions or the ATP-Fe(2+) complex catalyze selective cleavage of the alpha subunit of gastric H(+),K(+)-ATPase. The electrophoretic mobilities of the fragments and dependence of the cleavage patterns on E(1) and E(2) conformational states are essentially identical to those described previously for renal Na(+),K(+)-ATPase. The cleavage pattern of H(+),K(+)-ATPase by Fe(2+) ions is consistent with the existence of two Fe(2+) sites: site 1 within highly conserved sequences in the P and A domains, and site 2 at the cytoplasmic entrance to trans-membrane segments M3 and M1. The change in the pattern of cleavage catalyzed by Fe(2+) or the ATP-Fe(2+) complex induced by different ligands provides evidence for large conformational movements of the N, P, and A cytoplasmic domains of the enzyme. The results are consistent with the Ca(2+)-ATPase crystal structure (Protein Data Bank identification code; Toyoshima, C., Nakasako, M., Nomura, H., and Ogawa, H. (2000) Nature 405, 647-655), an E(1)Ca(2+) conformation, and a theoretical model of Ca(2+)-ATPase in an E(2) conformation (Protein Data Bank identification code ). Thus, it can be presumed that the movements of N, P, and A cytoplasmic domains, associated with the E(1) <--> E(2) transitions, are similar in all P-type ATPases. Fe(2+)-catalyzed cleavage patterns also reveal sequences involved in phosphate, Mg(2+), and ATP binding, which have not yet been shown in crystal structures, as well as changes which occur in E(1) <--> E(2) transitions, and subconformations induced by H(+),K(+)-ATPase-specific ligands such as SCH28080.
Shin
J M
JM
Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
Goldshleger
R
R
Munson
K B
KB
Sachs
G
G
Karlish
S J
SJ
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D000252:Calcium-Transporting ATPases / Q000737:chemistry / Q000378:metabolism; D002384:Catalysis; D005296:Ferrous Compounds / Q000378:metabolism*; D017506:H(+)-K(+)-Exchanging ATPase / Q000378:metabolism*; D006868:Hydrolysis; D008958:Models, Molecular; D010084:Oxidation-Reduction; D011487:Protein Conformation; D013552:Swine
D005296:Ferrous Compounds; D017506:H(+)-K(+)-Exchanging ATPase; D000252:Calcium-Transporting ATPases