Amino acid sequence elucidation of human acrosin-trypsin inhibitor (HUSI-II) reveals that Kazal-type proteinase inhibitors are structurally related to β-subunits of glycoprotein hormones

The amino acid sequence of the acrosin-trypsin inhibitor HUSI-II from human seminal plasma is presented which unequivocally identifies HUSI-II as being of Kazal-type. In addition, the HUSI-II sequence shows a striking similarity to the middle part of glycoprotein hormone β-subunits thus revealing a hitherto unknown structural and evolutionary relationship between Kazal-type inhibitors and glycoprotein hormone