Abstract
We have cloned the cDNAs encoding for the LH and FSH beta -subunits from a number of commercially important fish species, including seabream, mullet, tilapia and black carp. The cDNAs were used as probes to study gonadotropin gene expression, to isolate corresponding genes and to produce recombinant proteins. For the latter, beta LH and beta FSH cDNA sequences were introduced into both bacterial and baculovirus expression systems. The bacterial system yielded milligram amounts of recombinant proteins that were refolded in vitro, yet still gave a non-parallel response in an immunoassay compared to the native hormone. Antibodies against these recombinant proteins were used in western blots and ICC, but could not identify blood circulating levels of LH or FSH. The recombinant gonadotropins produced by the baculovirus expression system appear to be immunologically similar to the native hormones, as judged by their parallelism in immunoassays. The difficulties associated with this system are the low levels of production and purification from the culture media.