CLONING OF A CDNA FOR A NOVEL INSULIN-LIKE PEPTIDE OF THE TESTICULAR LEYDIG-CELLS

We have isolated complementary DNA clones coding for a novel member of the insulin-like hormone superfamily from a boar testis cDNA library. Northern blot analysis and in situ hybridization revealed that the ge ne is expressed exclusively in prenatal and postnatal Leydig cells. We have tentatively proposed the name Leydig insulin-like (Ley I-L) for the gene and its encoded protein. The Leydig insulin-like protein is s ynthesized as a 131-amino acid preproprotein, which contains a 24-amin o acid signal peptide. Comparison of the deduced amino acid sequence o f pro-Leydig insulin-like protein with members of the insulin-like hor mone superfamily predicts that the biologically active protein, after proteolytic processing of the C-peptide, consists of a 32-residue-long B-chain and a 26-residue-long A-chain and has a molecular size of 6.2 5 kDa.