THE COMPLETE AMINO-ACID-SEQUENCE OF HUMAN PLACENTAL OXYTOCINASE

The complete amino acid sequence of human placental oxytocinase (place ntal leucine aminopeptidase) has been determined by cDNA cloning and s equencing. Oxytocinase is a type II integral membrane protein of 1025 amino acid residues, consisting of an acidic intracellular region of 1 10 amino acids followed by a hydrophobic transmembrane segment of 22 r esidues and 893 extracellular residues containing the characteristic Z n2+ coordination sequence element His-Glu-Xaa-Xaa-His-(18 residues)-Gl u found in gluzincins. Two sets of cDNA clones with different 5'-ends were isolated and suggested to represent different spliced products of 3.6 kb (mature mRNA) and 12 kb, respectively. Oxytocinase mRNA is pre sent in large amounts in placenta, heart and skeletal muscle and in sm all amounts in brain, kidney, liver and pancreas. A conserved sequence element, the GAMEN motif, which distinguishes the aminopeptidase fami ly among gluzincins from other gluzincins, has been identified.