Abstract
This study was conducted to investigate new sperm molecules for immunocontraceptive vaccines and to provide data on baboon (Papio anubis) as an alternative animal model for human. Several molecules on the human sperm membrane were detected by cross-reactive antiserum to baboon sperm antigens on two-dimensional electrophoresis and western blotting. One of them, a protein of 25 kDa and pl range 4.8-5.0, was found to be homologous in its N-terminal amino acid sequences to the 78 kDa human glucose-regulated protein precursor (GRP78) and heat shock protein 70 (HSP70). In western blot analysis using an antibody to the N-terminal region of GRP78, human sperm showed an additional smaller MW band as well as the ordinary GRP78 band. Northern blot analysis revealed that a ~1.3kb mRNA transcript in the human epididymis differed from the ordinary size (~6.0kb) of GRP78. Collectively, the smaller molecule related to GRP78 is specifically expressed in the epididymis and transferred to sperm during transit through male reproductive tracts. This new variant should be further investigated as to the role of sperm and epididymal functions.
