COMPLETE SEQUENCE OF RABBIT KIDNEY AMINOPEPTIDASE-N AND MESSENGER-RNALOCALIZATION IN RABBIT KIDNEY BY IN-SITU HYBRIDIZATION

We have isolated and sequenced a full-length cDNA for rabbit kidney am inopeptidase N (APN). The 3-kilobase cDNA contains 12 nucleotides of t he 5' noncoding region, a 2898 nucleotide long open reading frame, and 113 nucleotides of the 3' untranslated region. The open reading frame encodes a type II membrane protein of 966 amino acid residues compose d of a 10 residue NH2-terminal cytosolic domain, a 23 residue transmem brane domain, and a large 933 residue ectodomain that contains the act ive site. Rabbit APN has eight potential N-glycosylation sites and sev en cysteine residues, one of which is located in the transmembrane dom ain. Computer analysis showed that the enzymes from human, rat, and ra bbit were highly conserved, except for the stalk region immediately do wnstream from the transmembrane domain. Using in situ hybridization te chniques we showed that in rabbit kidney, APN mRNA is present in proxi mal tubules but not in glomeruli, which corresponds to the localizatio n of the protein observed by immunohistochemistry. Taken together, our results strongly suggest that the expression of APN in kidney is modu lated at mRNA levels and not at translational and (or) posttranslation al levels.