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

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 -7.4x10(-5) (for the mucin) to -0.64x10(-5)cm(2)V(-1)s(-1). 3. Ultracentrifugal sedimentation values of s(20,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 (D(20,w) -1.57x10(-8)cm(2)/s). 4. Calculation of the approximate molecular weight from comparable s(20,w) and D(20,w) values gave a provisional value of 6.5x10(6). 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. 2.8x10(4)) cross-link with the long molecules of the mucin to form the seminal gel.