MOLECULAR-CLONING OF BOMAPIN (PROTEASE-INHIBITOR-10), A NOVEL HUMAN SERPIN THAT IS EXPRESSED SPECIFICALLY IN THE BONE-MARROW

Serine proteinase inhibitors or serpins are a superfamily of homologou s proteins that are for the most part involved in the regulation of pr oteolytic processes in a variety of biological systems. Utilizing a po lymerase chain reaction-based strategy we have cloned a novel member o f the ovalbumin family of serpins from a human bone marrow cDNA librar y. The new gene encodes a 397-amino acid protein, designated bomapin, with a calculated molecular mass of 45 kDa and 48% amino acid identity with plasminogen activator inhibitor-2, human leukocyte elastase inhi bitor, and cytoplasmic antiproteinase. A single 2.3-kilobase bomapin t ranscript is highly expressed in human bone marrow cells but was undet ectable in all other analyzed human tissues. lie vitro transcription a nd translation of the bomapin cDNA revealed the synthesis of an approp riately sized protein that was able to form SDS-stable complexes with thrombin and trypsin. The restricted expression of bomapin to the bone marrow raises the possibility that this serpin may play a role in the regulation of protease activities during hematopoiesis.