CDNA CLONING AND MEMBRANE TOPOLOGY OF THE RABBIT GASTRIC H+/K+-ATPASE ALPHA-SUBUNIT

We have cloned and sequenced a cDNA for the rabbit gastric proton-potassium pump (H+/K+-ATPase) alpha-subunit. The deduced peptide contains 1035 amino acids (M(r) 114201) and shows 97% sequence identity with the respective rat and hog proteins. A monoclonal antibody 146-14 has been shown previously to react with thc extracytoplasmic side of the catalytic H+/K+-ATPase subunit and here we show that the epitope is in the region between amino acids 855 and 902 (the numbering of the H+/K+-ATPase catalytic subunit throughout the paper refers to thc rabbit sequence). The localization of this epitope in conjunction with previously observed trypsin cleavage sites in the C-terminal one third of the enzyme and the hydrophobicity plot of the deduced peptide sequence are evidence for a structural model for the alpha-subunit of the H+/K+-ATPase which contains at least ten membrane spanning segments, similar to that deduced for the Ca2+-ATPase of sarcoplasmic reticulum.