Abstract
The copulatory vaginal plug is a conspicuous feature of rodent reproduction. The five major seminal vesicle secretory proteins of Rattus norvegiens (proteins I–V), which form the copulatory plug, constitute a closely related androgen-regulated family that appears to share a common evolutionary origin. The relationships between these rat proteins and the major seminal vesicle proteins of other rodents were explored using antibodies specific for the individual rat proteins. Immunoblotting of proteins separated by SDS-PAGE showed that the vesicular proteins of R. rattus are identical to those of R. norvegicus except for an additional protein related to protein III. No differences were seen in inbred and outbred strains of R. norvegicus. Of the major proteins of Mus musculus, one showed strong homology with rat protein II and three others were weakly homologous to proteins I, IV (or S) and V (or F); none showed homology to rat protein III. The only homology between the vesicular proteins of Mesocricetus auratus (Syrian hamster) and Meriones ungulatus (Mongolian gerbil) was with rat protein II while those of Cavia porcellus (guinea pig) showed no homology at all with the rat proteins. In addition, cDNA probes for rat genes IV and V both detected weak homologues in seminal vesicle RNA from mice but not guinea pigs. The results support our previous hypothesis that genes IV and V have evolved neutrally since their divergence before the rodent radiation (McDonald C.J. et al. (1984) EMBO J. 3, 2517–2521). In addition, we conclude that protein II is more highly conserved than IV and V, homologues being present in all Myomorpha tested, and that the genes for proteins I and III (and IIIA/B in R. rattus) arose from gene II during evolution of the Murid branch of the Myomorpha.
Published Version
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