Cloning and sequencing of goldfish activin subunit genes: strong structural conservation during vertebrate evolution

Inhibin and activin are structurally related dimeric peptides sharing two distinct but related subunits, beta A and beta B. By using polymerase chain reaction (PCR), we have cloned and sequenced activin beta A and beta B genes encoding the mature region of the peptides from the goldfish genomic DNA. A single form of beta A and two forms of beta B subunits were found. There is high identity with mammalian counterparts; the goldfish beta A subunit has 78% protein sequence identity with human beta A subunit, and the two beta B subunits have more than 94% sequence identity with human beta B subunit. This is the first demonstration of the activin family of peptides in the fishes.