Complementary deoxyribonucleic acid cloning and sequence analysis of the alpha-subunit of inhibin from chicken ovarian granulosa cells.

Using a porcine inhibin alpha-subunit cDNA as a probe, we have isolated four inhibin alpha-subunit cDNA clones (cINA6, cINA7, cINA9, and cINA12) from a cDNA library constructed from chicken ovarian granulosa layer mRNA. These four clones shared a common 3' end, and cINA6 (1585 bp) contains a complete open reading frame encoding for chicken inhibin alpha-subunit. The chicken inhibin alpha-subunit is predicted to be synthesized as a large precursor of 328 amino acids including a signal peptide region and several possible proteolytic sites. The mature alpha-subunit is the carboxyl-terminal fragment of 113 amino acids containing one glycosylation site and seven cysteine residues. Northern analysis of total RNA from various tissues revealed that chicken inhibin alpha-subunit mRNA is approximately 1.7 kb. It is present in the ovarian granulosa layer but not in the brain, kidney, liver, or spleen. The cDNA and its predicted polypeptide of chicken inhibin alpha-precursor are considerably homologous to their mammalian counterparts (86-89% and 61-63%, respectively).