Pig gastric (H+ + K+)-ATPase. Lys-497 conserved in cation transporting ATPases is modified with pyridoxal 5'-phosphate.
Pig gastric (H+ + K+)-ATPase can be covalently modified with pyridoxal 5'-phosphate (PLP) (about 1 mol/mol enzyme), and this modification is not observed in the presence of ATP, suggesting that PLP binds to a specific Lys residue in the ATP binding site or the region in its vicinity (Maeda, M., Tagaya, M., and Futai, M. (1988) J. Biol. Chem. 263, 3652-3656). The peptides labeled with radioactive PLP could be released from the gastric membrane vesicles quantitatively by chymotrypsin treatment, and two peptides were purified by high performance liquid chromatographies. These peptides were not obtained from vesicles incubated with PLP in the presence of ATP. The sequences of the two peptides were NH2-Asn-Ser-Thr-Asn-Lys-Phe-COOH and NH2-Ser-Thr-Asn-Lys-Phe-COOH, exactly corresponding to residues 493-498 and 494-498, respectively, of pig gastric (H+ + K+)-ATPase sequenced recently (Maeda, M., Ishizaki, J., and Futai, M. (1988) Biochem. Biophys. Res. Commun. 157, 203-209). Lys-497 was concluded to be the binding site of PLP, as pyridoxyl-Lys was identified at the corresponding position. This Lys residue is conserved in (Na+ + K+)- and Ca2+-ATPases. The possible amino acid residues in the catalytic site of gastric (H+ + K+)-ATPase are discussed.
Tamura
S
S
Department of Organic Chemistry and Biochemistry, Osaka University, Japan.
Tagaya
M
M
Maeda
M
M
Futai
M
M
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000201:enzymology; D004789:Enzyme Activation; D005753:Gastric Mucosa / Q000201:enzymology*; D005768:Gastrointestinal Hormones / Q000302:isolation & purification / Q000378:metabolism*; D008239:Lysine; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000302:isolation & purification; D011732:Pyridoxal Phosphate / Q000494:pharmacology*; D013552:Swine
D005768:Gastrointestinal Hormones; D010446:Peptide Fragments; C052257:hydrogen potassium ATPase, gastric endogenous activator protein, mammal; D011732:Pyridoxal Phosphate; D000251:Adenosine Triphosphatases; D008239:Lysine