Amino acid sequence deduced from a rat kidney cDNA suggests it encodes the Zn-peptidase aminopeptidase N

We have isolated and characterized rat kidney cDNA clones encoding a 140-kDa glycoprotein that exhibits characteristics of a cell surface Zn-peptidase. Structural features predicted for this putative kidney Zn-peptidase (KZP) are most consistent with properties previously determined for the Zn-peptidase aminopeptidase N. The deduced amino acid sequence of rat KZP is almost identical to the NH2-terminal sequence of aminopeptidase N purified from rabbit. The overall amino acid composition predicted for rat KZP is remarkably similar to that previously determined for rabbit and pig aminopeptidase N. The predicted Mr of rat kidney KZP approximates the Mr of the unglycosylated form of aminopeptidase N. The topology predicted for KZP is identical to that observed for aminopeptidase N: a short cytoplasmic domain at the NH2 terminus immediately precedes an uncleaved signal/anchor domain; a stalk region connects this membrane anchor to the extracellular, hydrophilic bulk of the protein containing catalytic sites required for Zn-peptidase activity. In addition, mRNA encoding KZP is present in tissues known to exhibit aminopeptidase N activity. Taken together with the observation that only a single gene homologous to KZP DNA is present in the rat and human genomes, these results suggest that we have established the primary structure of rat kidney aminopeptidase N.