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 hormones