Solution structure of seminal plasmin in the presence of micelles

The 47-amino-acid peptide seminal plasmin maintains a random-coil characteristic feature when in aqueous solution, as can be shown by CD and NMR measurements. However, upon binding to a hydrophobic/hydrophilic interface, an increase in the content of secondary structure is observed. This change in conformation can also be induced with the addition of a detergent. The secondary structure segments thus formed were assigned by two-dimensional NMR. The results indicate that hydrophobic interactions are a driving force in the folding of seminal plasmin. The interaction of seminal plasmin with detergent micelles could serve as a model for the binding of this interesting protein with the acrosome membrane of sperm cells.