EQUINE LEUKOCYTE ELASTASE INHIBITOR - PRIMARY STRUCTURE AND IDENTIFICATION AS A THYMOSIN-BINDING PROTEIN

The primary structure of an elastase inhibitor located in the cytoplas m of leukocytes obtained from the equine species has been determined. By sequence comparison, the protein was found to be a member of the se rpin family with strong identity to plasminogen activator inhibitor-2. In contrast to other serpins this protein contained no carbohydrate a nd had a blocked amino terminus. Preliminary evidence indicates that t he inhibitor has the additional feature of being a thymosin beta(4)-bi nding protein, since this polypeptide was always located in purified p reparations of the protein. This suggests a physiological role for cyt oplasmic elastase inhibitors in the thymosin beta(4)-regulated rearran gement of the cytoskeleton of leukocytes.