Studies of the bulbo-urethral (Cowper's)-gland mucin and seminal gel of the boar

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Abstract
1. Moving-boundary electrophoresis of the mucin from the Cowper's gland of the boar revealed a sharp single peak at pH values from 1.1 to 9.0 and an isoelectric point of 1.1. 2. Neuraminidase treatment of the mucin, which removed at least 96% of the sialic acid groups, decreased the electrophoretic mobility at pH4 from −7.4×10−5 (for the mucin) to −0.64×10−5cm2V−1s−1. 3. Ultracentrifugal sedimentation values of s20,w showed a marked dependence on concentration. A hyperfine peak, similar to that given by ovine submaxillary secretion, persisted throughout the run at higher concentrations. Ultracentrifugal studies further showed a very low value for the diffusion coefficient (D20,w −1.57×10−8cm2/s). 4. Calculation of the approximate molecular weight from comparable s20,w and D20,w values gave a provisional value of 6.5×106. 5. Two proteins present in the boar vesicular secretion known as protein A and protein H (the haemagglutinating protein) were shown to promote the swelling of the mucin to form the characteristic rigid elastic gel of boar semen. It is suggested that protein A molecules particularly (mol.wt. 2.8×104) cross-link with the long molecules of the mucin to form the seminal gel.