Title : Biosynthesis and molecular cloning of
sulfated glycoprotein 2 secreted by rat Sertoli cells
Abstract :
- Sulfated glycoprotein 2 ( SGP-2 ) is the major protein secreted by rat Sertoli cells
- Pulse-chase labeling shows that SGP-2 is synthesized as a cotranslationally glycosylated 64-kDa precursor that is modified to a negatively charged 73-kDa form before intracellular cleavage to the mature 47- and 34-kDa subunits
- A plasmid cDNA library was constructed from immunopurified mRNA, and a recombinant clone containing the entire protein coding sequence of SGP-2 was isolated
- The 1857-nucleotide cDNA consists of a 297-nucleotide 5' noncoding segment, a 1341-nucleotide coding segment, and a 219-nucleotide 3' noncoding sequence
- The 5' noncoding region contains five ATG codons followed by four short open reading frames
- The derived SGP-2 sequence has a molecular weight of 51,379 and contains six potential N-glycosylation sites
- Proteolytic processing sites for the prepro protein were determined by amino-terminal sequencing of the isolated SGP-2 subunits
- Northern blots show a wide tissue distribution for the 2.0-kb SGP-2 message, and computer sequence analysis indicates a significant relationship between SGP-2 and human apolipoprotein A-I