THE CLONING OF A RAPIDLY EVOLVING SEMINAL-VESICLE-TRANSCRIBED GENE ENCODING THE MAJOR CLOT-FORMING PROTEIN OF MOUSE SEMEN

Approximately 30 kb of the mouse genome, containing the gene for a maj or seminal vesicle transcript, has been cloned. The gene was identifie d by the similarity to members of a family with rapidly evolving genes that includes the gene encoding the major clot protein in rat semen, SVS II, and the human semenogelin genes. The nucleotide sequence of 16 .9 kb was determined; this sequence encompasses the gene of 2215 bp pl us 9-kb and 5.6-kb regions flanking the 5' and 3' ends of the gene. Th e transcription unit is divided into three exons, of which the first e ncodes the signal peptide, the second the secreted protein, while the third exon contains 3'-nontranslated nucleotides only. The transcript encodes a protein of 375 amino acid residues, including a signal pepti de of 22 residues. The secreted polypeptide is a protein of M(r) 38442 and is similar in sequence but smaller than the major clot-forming pr otein of rat semen: SVS II. It is highly charged at pH 7 and it has an isoelectric point of 10.68. The central part of the protein consists of tandem repeats that might serve as a substrate for transglutaminase .