We have isolated and sequenced the cDNA and gene coding for a novel me
mber of the insulin-like hormone superfamily. The gene is expressed ex
clusively in prenatal and postnatal Leydig cells and in postnatal ovar
y. We have tentatively proposed the name Leydig insulin-like (Ley I-L)
for the gene and its encoded protein. The porcine Leydig insulin-like
protein is synthesized as a 131-amino acid preproprotein, which conta
ins a 24 amino acid signal peptide. Comparison of the deduced amino ac
id sequence of pro-leydig insulin-like protein predicts that the biolo
gically active protein, after proteolytic processing of the C-peptide,
consists of a 32 residue-long B-chain and a 26-residue-long A-chain.
Western blot analyses with antiserum against a synthetic oligopeptide
containing the amino acid sequence of the B-chain confirm the proteoly
tic processing of the pro-ley I-L peptide. Furthermore, we describe he
re the initial analysis of the Ley I-L gene promoter by transient gene
transfer studies. We show that the sequence between -186 and +13 of t
he porcine Ley I-L gene contains sufficient information to direct pref
erential expression of the chloramphenicol-acetyltransferase (CAT) rep
orter gene in Leydig cells and sequences important for negative regula
tion of Ley I-L promoter activity are contained in the region between
-960 and -186.