Structural properties of semenogelin I.
The zinc-binding protein semenogelin I is the major structural component of the gelatinous coagulum that is formed in freshly ejaculated semen. Semenogelin I is a rapidly evolving protein with a primary structure that consists of six repetitive units, each comprising approximately 60 amino acid residues. We studied the secondary and tertiary structure of semenogelin I by circular dichroism (CD) spectroscopy and Trp fluorescence emission spectroscopy. Fitting to the far-UV CD data indicated that the molecule comprises 5-10% alpha-helix and 20-30% beta-sheet formations. The far-UV spectrum of semenogelin I is clearly temperature dependent in the studied range 5-90 degrees C, and the signal at 222 nm increased with increasing temperature. The presence of Zn(2+) did not change the secondary structure revealed by the far-UV CD spectrum, whereas it did alter the near-UV CD spectrum, which implies that rearrangements occurred on the tertiary structure level. The conformational change induced in semenogelin I by the binding of Zn(2+) may contribute to the ability of this protein to form a gel.
Malm
Johan
J
Department of Laboratory Medicine, Section for Clinical Chemistry, Lund University, Malmö University Hospital, Sweden.
Jonsson
Magnus
M
Frohm
Birgitta
B
Linse
Sara
S
D006801:Humans; D011487:Protein Conformation; D029607:Seminal Vesicle Secretory Proteins / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods
D029607:Seminal Vesicle Secretory Proteins; C424482:seminal vesicle-specific antigen